Image display systems having direct and projection viewing modes

ABSTRACT

A transportable image display system having direct and projection viewing modes of operation. The image display system comprises a spatial light modulation structure for spatially modulating the intensity of light produced from a light source, and light diffusing panel of electro-optical construction having a light scattering state in which light being transmitted therethrough is scattered in a diffusive manner, and a light transmission state in which light being transmitted therethrough is transmitted without substantial scattering. In the illustrative embodiments, the spatial light modulation structure can be an electrically-addressable LCD panel, or slide-film structures to be viewed. During the direct viewing mode, light produced from the light source is scattered by the light diffusing panel and spatial intensity modulated by the spatial light modulation structure to form a first image for direct viewing. During the projection viewing mode, light produced from the light source is transmitted through the light diffusing panel without substantial scattering and spatial intensity modulated by the spatial light modulation structure to form a second image for projection onto a projection display surface for projection viewing.

RELATED CASES

This is a Continuation of application Ser. No. 08/563,520 filed Nov. 28,1997, now U.S. Pat. No. 5,680,233, which is a Continuation-in-Part ofapplication Ser. No. 08/322,219 entitled "BACKLIGHTING CONSTRUCTION FORUSE IN COMPUTER-BASED DISPLAY SYSTEMS HAVING DIRECT AND PROJECTIONVIEWING MODES OF OPERATION" by Sadeg M. Faris, et al., filed Oct. 13,1994, which is a continuation-in-part of application Ser. No. 08/230,779entitled "ELECTRO-OPTICAL BACKLIGHTING PANEL FOR USE IN COMPUTER-BASEDDISPLAY SYSTEMS AND PORTABLE LIGHT PROJECTION DEVICE FOR USE THEREWITH"by Sadeg M. Faris, filed Apr. 21, 1994, now U.S. Pat. No. 5,784,130,both of which are incorporated herein by reference as if set forth fullyherein.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to transportable systems having bothdirect and projection viewing modes of operation, and to electro-opticalbacklighting panels for use therein.

2. Brief Description of the State of the Art

Presently, most portable computing systems include a flat liquid crystaldisplay (LCD) panel for directly viewing video imagery displayedthereon. Portable computer systems of this type include notebook,laptop, and palmtop computers.

In general, prior art LCD display panels have essentially the same basicconstruction in that each includes a conventional backlighting structureaffixed to the rear surface of either a passive or active matrix LCDpanel. Several different backlighting panel designs are described in thetechnical paper "New Backlighting Technologies for LCDs" by Kevin J.Hathaway, et al., published at pages 751-754 in SID 91 Digest. In recenttimes, the "light pipe" backlight design, in particular, has been widelyused in many commercially available notebook computers.

Specifically, prior art "light pipe" backlight assemblies areconstructed from a rectangularly shaped light guiding panel, typicallyfabricated from an acrylic plastic sheet having a thickness of about 4millimeters or so. Along the opposite side edges of the acrylic sheet, apair of miniature fluorescent light tubes are mounted within suitablydesigned light reflective mounts. The function of the fluorescent lighttubes is to produce and direct incoherent light into the interior of thelight guiding panel within which the light is typically bounded by thewell known principle of "total internal reflection". Under idealconditions, light will not leak out of the surfaces of the acrylicplastic sheet. However, light can be extracted or leaked out from thesesurfaces by forming therein scratches, undulations, or any other meansof locally altering the critical angle for total internal reflection. Byachieving light extraction in this manner, the backlighting panel can beused to illuminate an LCD panel.

In order to compensate for the decrease in light intensity in the lightguiding panel at distances away from the fluorescent tubes, a lightextracting pattern is permanently formed on one or both surfaces of thelight guiding panel. Typically the light extracting pattern is realizedas a dot pattern permanently embossed or sand-blasted upon the frontsurface of the acrylic light guiding panel. The density of the dotpattern is made to increase quadratically with distance from thefluorescent light tubes in order to achieve light intensity compensationalong the light guiding panel. With this construction, a constantbacklighting brightness is maintained across the light guiding panel.

In order to integrate (i.e. diffuse) the spotted distribution of lightemanating from the light extracting pattern towards the LCD panel, afirst light diffusing structure is placed on top of the light guidingpanel. Typically, the first light diffusing structure is made from oneor more thin sheets of translucent plastic attached to the front surfaceof the light guiding panel. In most commercial "light pipe" backlightdesigns, a second light diffusing structure is placed over the rearsurface of the light guiding panel to diffuse the spotted distributionof light emanating from the permanently formed light extracting patterntowards the reflective surface disposed behind the light guiding panel.Typically, the second light diffusing structure is made from one or morethin sheets of translucent plastic attached to the rear surface of thelight guiding panel. Together, the light guiding panel, fluorescentlight tubes, light diffusing sheets and the light reflective layercooperate to produce a plane of backlight having a uniform spatialintensity for optical processing by the LCD panel affixed to thebacklighting panel.

While the prior art backlighting panel design described above has provenuseful in the direct viewing of visual imagery on LCD display screens,its permanently formed light extracting pattern renders it unsuitable inprojection viewing modes of operation. This fact is best illustrated byexample.

In the recently introduced notebook computer, marketed under thetradename "Cruiser™" by EMCO/REVERED Technologies, Inc. and generallydescribed in U.S. Pat. No. 5,353,075 to Conner, et al., theabove-described "light pipe" backlighting panel design is used toconstruct a portable computer system having both direct and projectionviewing modes of operation. In the direct viewing mode, the prior artbacklighting panel is positioned against the active-matrix LCD panel.Each time the user desires to operate the notebook computer in itsprojection viewing mode, the user must mechanically reconfigure theCruiser™ notebook computer by physically removing the prior artbacklighting panel in order to reveal the active matrix LCD panel, andprovide an optically clear path for the light rays to pass therethrough.

Recently, Intellimedia, Corporation of Benton Harbor, Michigan hasintroduced the IntelliMedia™ Multimedia Presentation System whichconsists of portable computer system having a flat LCD projection panelwhich can support both direct and projection viewing modes. In thedirect viewing mode, the user of this system is required to affix anauxiliary backlighting panel beneath the LCD panel. Then, when operatedin the projection viewing mode, the user is required to remove theauxiliary backlighting panel, and place the LCD panel upon an externaloverhead projector, much like that required by the Cruiser™ computersystem.

While the above-described image display systems provide both direct andprojection viewing modes, they both nevertheless suffer from a number ofserious shortcomings and drawbacks which make them less thancommercially attractive products.

In particular, the need to physically remove the entire backlightingpanel from the Cruiser™ computer during its projection viewing mode,poses a substantial risk of damage to the backlighting panel and imposesan added responsibility upon the user to safely store the same when thecomputer system is operated in its projection viewing mode. Also, from apractical standpoint, the need to place the display panel assembly ofthe Cruiser™ computer and the entire display panel of the Intellimedia™system upon an overhead projector during projection viewing,necessitates that the user either tote an overhead projector along withsuch prior art systems, or have access to one during projection viewing.Consequently, such prior art image display systems lack the versatilityof operation in either direct or projection modes of viewing, and thusare incapable of functioning as truly portable systems.

Thus, there is a great need in the art for an improved image displaysystem which has direct and projection viewing modes, without theshortcomings and drawbacks of the prior art systems.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, a primary object of the present invention is to provide anovel electro-optical light panel construction particularly designed foruse in image display systems having both direct and projection viewingmodes of operation.

A further object of the present invention is to provide a portable imagedisplay system having direct and projection viewing modes.

A further object of the present invention is to provide an image displaysystem in the form of a portable computer-based system which can beeasily configured into its projection viewing mode using anelectro-optical light panel having light scattering and non-scatteringstates of operation selectable under electronic control.

A further object of the present invention is to provide a portabledevice for illuminating the electro-optical display panel of acomputer-based image display system having direct and projection viewingmodes, in order to project focused video images therefrom onto a desiredviewing surface.

A further object of the present invention is to provide a portablecomputer-based image display system with a rear housing panel that ishingedly connected to a light guiding panel and supports a lightreflective surface and covers the rear light transmission aperture whenthe system is operated in its direct viewing mode.

A further object of the present invention is to provide such a portablecomputer-based image display system, in which the display panel assemblythereof includes a thin light focusing panel, such a Fresnel orholographic lens panel, for use during the projection viewing mode.

A further object of the present invention is to provide such a portablecomputer-based image display system, in which a film slide or opticaltransparency carrying imagery can be placed upon the display surface ofthe display panel assembly thereof and the imagery viewed in either thedirect or projection viewing mode.

A further object of the present invention is to provide a flatelectro-optical display panel assembly having direct and projectionviewing modes of operation, and an electro-optical light panel having alight emission state in which light is emitted from the electro-opticalpanel during the direct viewing mode of operation, and a lighttransmission state in which externally generated light is permitted topass through the electro-optical panel without substantial scatteringduring the projection viewing mode of operation.

A further object of the present is to provide such a flat display panelassembly as described above, in which the light emission andtransmission states of the electro-optical light panel areelectronically selectable during the first and second modes ofoperation, respectively.

A further object of the present invention is to provide a flat displaypanel as described above, in which the electro-optical light panel isrealized as a polymer dispersed liquid crystal (PDLC) panel assemblyhaving a light-diffusive state of operation that is electronicallyselectable during the direct viewing mode, and also a lightnon-diffusive state of operation that is electronically selectableduring the projection viewing mode of operation, without removal orother physical modification of the light panel.

A further object of the present invention is to provide a flat displaypanel construction different from the display panel described above, inwhich the electro-optical light panel is realized as aelectroluminescent (EO) panel assembly having a layer ofelectroluminescent material that emits light from the panel during thedirect viewing mode, and permits externally generated light to passthrough the electro-luminescent panel during the projection viewing modewithout substantial scattering.

A further object of the present invention is to provide a novelcomputer-based image display system which incorporates such a displaypanel assembly construction, and can be easily reconfigured for itsprojection viewing mode of operation without physical modification tothe display panel assembly construction.

A further object of the present invention is to provide such a portablecomputer-based image display system with a housing having a lightaperture that permits an external source of intense light to passdirectly through the display panel assembly in order to project focusedvideo images therefrom onto a desired viewing surface.

A further object of the present invention is to provide such a portablecomputer-based image display system with a hinged housing panel disposedbehind the display panel assembly for supporting a light reflectivepanel and covering the light aperture when the system is operated in itsdirect viewing mode.

A further object of the present invention is to provide such a portablecomputer-based image display system, in which a film slide or opticaltransparency carrying imagery can be placed upon the display surface ofthe display panel assembly of the present invention and the imageryviewed in either the direct or projection viewing mode.

A further object of the present invention is to provide a portablecomputer-based image display system having both direct and projectionviewing modes of operation, in which "spatially-multiplexed" images of3-D objects or imagery are viewable through an LCD display panel duringthe direct viewing mode, and viewable on a wall surface or projectionscreen during the projection viewing mode, so as to permit the 3-Dobject to be perceived with stereoscopic depth sensation when thespatially-multiplexed images are viewed through polarized viewingspectacles.

A further object of the present invention is to provide a portable imagedisplay system having both direct and projection viewing modes ofoperation so that it is capable of selectively displaying color videoimages on its display surface during its direct viewing mode, andprojecting such video images onto a projection display surface duringits projection viewing mode.

A further object of the present invention is to provide a portablepen-computing device capable of supporting pen-based data entryoperations and stereoscopic image display in both direct and projectionviewing modes of operation.

A further object of the present invention is to provide a portable lightprojection accessory device that is particularly adapted for use withthe portable computer-based systems of the present invention.

A further object of the present invention is to provide such a portablelight projection device having first and second housing portions thatare interconnected by a foldable structure that permits these housingportions to be selectively reconfigured for use during the projectionviewing mode of operation, and for compact storage during the directviewing mode of operation.

A further object of the present invention is to provide such a portablelight projection device, wherein the first housing portion contains anintense light source and a light polarizing filter for producing anintense source of polarized light, and an optics assembly for projectingthe produced polarized light, and wherein the second housing portioncontains an image projection lens that can be adjustably positioned withrespect to the display panel assembly thereof for projecting a focusedvideo image onto a desired viewing surface.

A further object of the present invention is to provide a method ofprojecting images from such a portable computer-based system, by movingthe rear housing panel away from the display panel assembly, positioningan external projection lens in front of the display panel assembly,electrically selecting the projection viewing mode of operation for thedisplay assembly, and projecting an intense source of polarized lightthrough the display panel assembly so that when the intense polarizedlight rays pass through the display panel assembly and are opticallyprocessed thereby and focused by the projection lens, a focused videoimage is projected onto a desired viewing surface.

An even further object of the present invention is to provide such acomputer-based image display system in the form of either a palmtop,laptop or notebook computer, personal digital assistant or personalcommunicator which, with the portable light projecting device hereof,can be easily stored and transported in a lightweight carrying casehaving physical dimensions on the same order as the portable computeritself.

These and other objects of the present invention will become apparenthereinafter and in the Claims to Invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, the DetailedDescription of the Illustrative Embodiments of the Present Invention isto be read in conjunction with the following drawings, in which:

FIG. 1 is a first perspective view of the portable computer-based systemof the first illustrative embodiment of the present invention, shownarranged in its direct viewing configuration;

FIG. 1A is a second perspective view of the portable computer-basedsystem of FIG. 1, shown arranged in its direct viewing configuration;

FIG. 2 is a block system diagram of the portable image display systemshown in FIGS. 1 and 1A;

FIG. 3 is a schematic representation of the image display subsystem ofthe portable computer system of the first illustrative embodiment, shownin its direct viewing configuration;

FIG. 3A is a cross-sectional view of the display panel assembly of thefirst illustrative embodiment, taken along line 3A--3A of FIG. 3,showing the electro-optical light diffusing panels thereof beingconstructed in accordance with a first manufacturing technique;

FIG. 3B is a cross-sectional view of the display panel assembly of thesecond illustrative embodiment, taken along line 3B--3B of FIG. 3,showing the electro-optical light diffusing panels thereof beingconstructed in accordance with a second manufacturing technique;

FIG. 3C is an enlarged cross-sectional view of a portion of anelectro-optical light diffusing panel in the display panel assembly ofFIG. 3, shown during the direct viewing mode;

FIG. 3D is a schematic representation of an electrode pattern formed onone of the surfaces of the light guiding structure of the display panelassembly of FIGS. 3A or 3B in order to achieve light intensitycompensation thereacross during the direct viewing mode;

FIG. 3E is a cross-sectional view of the light guiding structureemploying the electrode pattern of FIG. 3D;

FIG. 3F-3H are steps diagrams of a third method of light intensitycompensation;

FIG. 4 is a perspective view of the portable computer-based system ofthe first illustrative embodiment, shown arranged in its firstprojection viewing configuration;

FIG. 4A is an elevated side view of the portable computer-based systemof the first illustrative embodiment, shown arranged in its firstprojection viewing configuration;

FIG. 4B is an elevated side view of the portable computer-based systemof the first illustrative embodiment, shown arranged in its secondprojection viewing configuration using an alternative embodiment of theportable light projecting device of the present invention;

FIG. 5 is a schematic representation of the image display subsystem ofthe portable computer system of the first illustrative embodiment, shownin its projection viewing configuration;

FIG. 5A is a cross-sectional view of the image display panel assembly ofthe first illustrative embodiment, taken along line 5A--5A of FIG. 5,showing the electro-optical light diffusing panels thereof beingconstructed in accordance with a first manufacturing technique of thepresent invention;

FIG. 5B is a cross-sectional view of the display panel assembly of thesecond illustrative embodiment, taken along line 5B--5B of FIG. 5,showing the electro-optical light diffusing panels thereof beingconstructed in accordance with a second manufacturing technique of thepresent invention;

FIG. 5C is an enlarged, cross-sectional view of a portion of anelectro-optical light diffusing panel in the display panel assembly ofFIG. 5, shown during the projection viewing mode;

FIG. 6A is a perspective view of the portable accessory device of thepresent invention, shown arranged in its compact storage configuration;

FIG. 6B is a perspective view of the portable light projection device ofthe present invention, shown partially extended but not completelyarranged in its light projecting and image focusing configuration;

FIG. 7 is a schematic diagram of the first housing portion of theportable light projecting device of the present invention, showingvarious subcomponents contained within this portion of the device;

FIG. 8 is a perspective view of the second housing portion of theportable light projecting device of the present invention, showing thevarious subcomponents contained within this portion of the device;

FIG. 9 is a first perspective view of the portable computer-based systemof the second illustrative embodiment of the present invention, shownconfigured for direct stereoscopic image viewing, and also illustratingthe removal of the light reflective back panel from the hinged displayportion of the housing;

FIG. 10 is a perspective view of the portable computer-based system ofthe second illustrative embodiment, shown arranged in its projectionviewing configuration, upon a conventional overhead image projector,with its light reflective back panel removed as shown in FIG. 9, forstereoscopic image projection;

FIG. 10A is an elevated side view of the portable computer-based systemof the second illustrative embodiment, shown arranged in its projectionviewing configuration, upon a conventional overhead image projector ofFIG. 10, for stereoscopic image projection;

FIG. 11 is a schematic representation of the image display subsystem ofthe portable computer-based system of FIG. 10, shown with its displaypanel assembly configured in its projection viewing mode of operation;

FIG. 11A is a cross-sectional view of the display panel assembly of thesecond illustrative embodiment of the present invention, taken alongline 11A--11A of FIG. 11, showing the electro-optical light diffusingpanels thereof being constructed in accordance with a firstmanufacturing technique of the present invention;

FIG. 11B is a cross-sectional view of the display panel assembly, takenalong line 11B--11B of FIG. 11, showing the electro-optical lightdiffusing panels thereof being constructed in accordance with a secondmanufacturing technique of the present invention;

FIG. 11C is an enlarged, cross-sectional view of a portion of theelectro-optical light diffusing panel in the display panel assembly ofFIG. 11, shown during the projection viewing mode;

FIG. 12 is a perspective view of the portable image display device ofthe present invention being used to directly view imagery recorded in afilm structure (e.g. film slide) while operated in its backlightingmode;

FIG. 12A is a perspective view of the image display device of FIG. 12,shown interfaced with a conventional computer system while beingoperated in its direct viewing mode;

FIG. 12B is a perspective view of the image display device of FIG. 12,shown interfaced with a conventional computer system while beingoperated in its projection viewing mode;

FIG. 12C is a cross-sectional view of the image display panel assemblyof the third illustrative embodiment, taken along line 12C--12C of FIG.12;

FIG. 12D is a cross-sectional view of the display panel assembly of thefourth illustrative embodiment, also taken along line 12C--12C of FIG.12;

FIG. 13 is a perspective view of the portable pen-computing device ofthe present invention, shown being used in its pen-type data entry modeof operation, and direct viewing modes of operation;

FIG. 13A is a cross-sectional view of the portable pen computing deviceof the present invention, taken along line 13A--13A of FIG. 13, showingin greater detail the construction of the display/touch-screen panelassembly employed therein;

FIG. 13B is a perspective view of the portable pen-computing device ofthe present invention, shown being operated in its projection viewingmode;

FIG. 14 is a perspective view of yet another embodiment of theelectro-optical backlighting panel of the present invention, realizedusing electroluminescent materials;

FIG. 14A is a cross sectional view of the electro-optical backlightingpanel of FIG. 14;

FIG. 15 is an elevated side view of a portable computer-based system ofanother illustrative embodiment of the present invention, shown arrangedin its projection viewing configuration;

FIG. 15A is a perspective view of the portable computer-based system ofFIG. 15, showing the image projection lens and removable supportstructure being removed from its internal storage compartment disposedbeneath the central lower base portion of the computer system;

FIG. 15B is a perspective view of the portable computer-based system ofFIG. 15, showing the image projection lens supported along theprojection axis of the display panel assembly hereof by way of theremovable support structure mounted with the support slot formed in thebase portion of the computer system;

FIG. 16 is a schematic diagram of a transportable image display systemof another illustrative embodiment of the present invention, having botha direct viewing mode of operation during which spatially-multiplexedimages are displayed on the surface of its electro-optical light panelfor stereoscopic 3-D viewing, and a projection viewing mode of operationduring which spatially-multiplexed images are projected onto aprojection viewing surface for stereoscopic 3-D viewing; and

FIG. 17 is a schematic diagram of a transportable image display systemof yet another illustrative embodiment of the present invention, havingboth a direct viewing mode of operation during whichspatially-multiplexed images are displayed on the surface of itselectro-optical light panel for stereoscopic 3-D viewing, and aprojection viewing mode of operation during which spatially-multiplexedimages are projected onto a projection viewing surface for stereoscopic3-D viewing.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

In general, the electro-optical light panel (e.g. backlighting panel) ofthe present invention can be used in various image display environments.For purposes of illustration, the light panel of the present inventionis shown incorporated as a component in various portable computer-basedsystems, namely: the portable notebook/laptop computer illustrated inFIGS. 1 to 5C; the portable notebook/laptop computer illustrated inFIGS. 9 to 11C; the portable image display device illustrated in FIGS.12 to 12E; the portable pen-computing device illustrated in FIGS. 13 to13B; the portable notebook/laptop computer illustrated in FIGS. 15 and15A; and the portable image display systems in FIGS. 16 and 17. It isunderstood, however, that the electro-optical backlighting panel of thepresent invention may be used with other types of computer-based systemsand equipment, including computer monitors, optical transparencies, filmstructures and the like, without departing from the scope and spirit ofthe present invention.

In general, the light panel of the present invention comprises anelectro-optical structure having a light emission state in which lightis emitted therefrom, and a light transmission state which permits theelectro-optical structure to pass externally generated lighttherethrough without substantial scattering. In many embodiments, theelectro-optical structure will be realized in the form of a thinelectro-optical panel having first and second modes of operation.Electronic circuitry is provided for selecting the light emission stateduring the first mode of operation, and the light transmission stateduring the second mode of operation. The electro-optical backlightingpanel is particularly suited for use in various applications wherebacklighting illumination is required or desired.

The electro-optical light panel of the present invention may be realizedin a variety ways, using a variety of technologies, without departingfrom the scope or spirit of the present invention. Such technology mayinclude, for example, the use of polymer-dispersed liquid crystal (PDLC)or electroluminescent (EO) materials, but of course is not limited tosuch electro-optical technologies.

In accordance with one illustrative embodiment of the present invention,the light panel is realized by integrating several components, namely: alight producing means; a light guiding structure; a light diffusingstructure, and a state selection means. The light guiding structure isformed from optically transparent material and has first and secondlight guiding surfaces and at least a first light conducting edge. Thefunction of the light producing means is to produce visible light fortransmission through the light conducting edge and internal reflectionbetween the first and second light guiding surfaces. The light guidingstructure. The light diffusing structure is operably associated with thelight guiding structure, and has a light scattering (i.e. diffusing)optically transparent state of operation which is selectable during thedirect viewing mode, and a light non-scattering optically transparentstate of operation which is selectable during the projection viewingmode. In this particular embodiment, the function of the state selectionmeans is to select the light scattering state during the direct viewingmode, and the light non-scattering state during the projection viewingmode. In the preferred embodiments of the present invention, the stateselection means is realized so as to enable electronic switching of thelight diffusing structure from its light scattering state of operation,to its light non-scattering state of operation.

During the direct viewing mode, a light reflective surface is disposedadjacent the second light guiding surface of the light guidingstructure, and the light producing means produces visible light fortransmission through the light conducting edge and into the lightguiding structure, wherein it is totally internally reflected betweenthe first and second light guiding surfaces thereof. In the directviewing mode, the state selection means electronically switches thelight diffusing structure to its the light scattering state ofoperation. While operated in its light scattering state, the lightdiffusing structure scatters light rays internally reflected within thelight guiding panel, and as such, a certain percentage of thesescattered light rays are no longer satisfy the conditions for totalinternal reflection within the light guiding panel. Consequently, thesescattered light rays are permitted to pass or leak through the firstlight guiding surface of the light guiding panel, and direct illuminateoptical transparencies, film structures, flat LCD panels and the like.

During the projection viewing mode, the light reflective surface is notdisposed adjacent the second light guiding surface of the lightdiffusing structure, and light is typically not produced from the lightproducing means. Rather, light is produced from an external light sourceand projected through the light guiding panel. Without physicallyremoving the light diffusing structure from the light guiding panel, thestate selection means electronically switches the light diffusingstructure to its the light non-scattering state of operation. Whileoperated in its light non-scattering state, the light diffusingstructure permits the projected light rays to pass freely through thelight guiding structure and light diffusing structure, withoutsubstantial scattering. Consequently, the projected light rays emergingfrom the backlighting panel can be used to illuminate opticaltransparencies, film structures, flat LCD panels and the like, andproject images on large viewing surfaces.

Alternatively, the electro-optical light panel of the present inventioncan be realized as an electroluminescent panel assembly having a layerof electroluminescent material that emits light from the panel duringthe direct viewing mode, and permits externally generated light to passthrough the electroluminescent panel during the projection viewing modewithout substantial scattering. With this alternative method ofconstruction, a special choice of electroluminescent materials, ratherthan PDLC materials, are used to achieve the light emission andtransmission states of the electro-optical light panel.

In general, the light panel of the present invention can be used in manydifferent applications requiring illumination of optical transparencies,film structures, flat LCD panels and the like. However, for purposes ofillustration only, light panel of the present invention will bedescribed in great detail with reference to several computer-basedembodiments described below.

With the above overview of the present invention in mind, theillustrative embodiments thereof will now be described in detail below.Notably, throughout the drawings, like figures shall be indicated withlike reference numbers.

As shown in FIGS. 1 and 1A, portable computer system 1 includes ahousing having a base portion 2 and a hingedly connected display (orcover) portion 3. As illustrated in FIG. 2, portable computer system 1comprises a number of integrated system components, namely: one or morecentral processing units 4 (e.g. microprocessors); high-speed randomaccess memory storage device (e.g. RAM) 5 for storing system parameters,operating system routines, application programs, and the like duringexecution; a high-speed read only memory device (e.g. ROM) 6 for storingportions of an operating system program; a hard-disc drive subsystem 7for reading and writing onto hard-type magnetic or opto-magnetic discs,information files, programs, image data and the like for long termstorage; a floppy-disc drive subsystem 8 for reading and writing ontofloppy-type magnetic discs, information files, programs, image data andthe like for long term storage; a visual display subsystem 9 including aLCD display panel assembly 10 and X and Y driver circuitry 11 shown inFIGS. 3 and 3A; a video image storage subsystem including a video randomaccess memory device (e.g., VRAM) 12 for buffering frames of video datato be displayed on the display panel assembly, and a display processor13 for accessing frames of video data stored in VRAM 12 and providingthese video frames to the X and Y driver circuitry 11; a keyboard orother text input device 14 and associated interface circuitry; apointing and selecting device (e.g. mouse or track-ball) 15 andinterface circuitry and an external input/output port 16 for interfacingone or more input or output devices, such as CD-ROM (optical disc)player, stereo-video camera, facsimile unit, and the like. Asillustrated, each of these system components is operably associated withprocessor(s) 4 by way of one or more system buses 17 in a manner knownin the art. In addition, the computer system also includes arechargeable battery pack 18 and power distribution circuitry 19 wellknown in the portable computing art.

In the preferred embodiment, the operating system may be realized byMacintosh® System 7.0 operating system software from Apple Computer,Inc., Windows® operating system software from Microsoft Corporation, orUNIX® X-Windows operating system software from AT&T, allowing theprocessors to support a plurality of input/output windows, pointing andselecting device 15, and multi-media input and output devices. It isunderstood, however, that other suitable operating system programs canbe used with acceptable results without departing from the scope andspirit of the present invention.

In the first illustrative embodiment of the computer-based system, allof the above-described system components, except for display panelassembly 10, are contained in the base portion of the computer housingshown in FIGS. 1 and 1A, and only display panel assembly 10 is mountedwithin the hinged cover portion of the housing. It is understood,however, the particular distribution of system components will vary fromembodiment to embodiment of the present invention.

As shown in FIGS. 1 and 1A, both the front and rear sides of cover 3have an rectangular light transmission apertures 20A and 20B formedtherethrough. The size of these apertures are substantially the same,yet slightly smaller in length and width dimensions than display panelassembly 10 of the present invention in order to support theperimetrical edges of the display panel assembly in a conventionalmanner known in the art. In the first illustrative embodiment, anoptically opaque rear panel 21 is hingedly connected to the rear portionof the cover so as to completely close off light transmission aperture20B when panel 21 is rotated downwardly into its direct viewingconfiguration shown in FIG. 1A. When rotated upwardly in order toarranged the portable computer into its projection viewing configurationas shown in FIG. 4, rear panel 21 is held in position at a 45 degreeangle with respect to the plane of display panel assembly 10. Thedimensions of rear panel 21 are slightly smaller than the dimensions ofthe rear aperture 20B.

As shown in the direct viewing configuration of FIGS. 3 and 3A, displaypanel assembly 10 is constructed by integrating a first illustrativeembodiment of the electro-optical backlighting panel of the presentinvention with a programmable spatial light modulator (SLM), realized asa conventional LCD panel 33. As illustrated in these drawings, the firstillustrative embodiment of the light panel comprises a number ofsubcomponents, namely: a light guiding structure 25 in the form of afirst polymer dispersed liquid crystal (PDLC) panel (25) consisting of apair of spaced apart, optically transparent panels 25A and 25B havingexteriorly disposed light guiding surfaces 25C and 25D and interiorlydisposed surfaces 25E and 25F, a uniformly thick layer ofpolymer-dispersed liquid crystal material 26 deposited between panels25A and 25B; a pair of fluorescent lighting tubes 27 and 28 electricallyconnected to power supply 19 and controlled by processor 4; elongatedconcave light reflectors 29 and 30; a second PDLC panel 31 affixed tothe front surface of light guiding structure 25 with an ultra-thin airgap 32 disposed therebetween; a third PDLC panel 34 affixed to the rearsurface of second PDLC panel 31 with an ultra-thin air gap 35therebetween; a fourth PDLC panel 36 affixed to the rear surface oflight guiding structure 25 with an ultra-thin air gap 37 therebetween;and a thin lens panel, realized as a Fresnel lens zone structure orholographic optical lens element in a thin optically transparent layer38 directed laminated onto the rear surface of the fourth PDLC panel 36,with an ultra-thin air gap 39 therebetween. Together, panels 25, 31, 34,36 and 38 form the electro-optical backlighting panel of the firstillustrative embodiment. As shown in FIG. 3A, active-matrix LCD displaypanel 33 is affixed to the rear surface of the front surface of secondPDLC panel 34 with an ultra-thin air gap 50 disposed therebetween.Alternatively, thin lens panel 38 may be disposed between second PDLCpanel 34 and LCD display panel 33 with an appropriate air gap formedbetween PDLC panel 34 and thin lens panel 38. As such, panels 25, 31,33,34, 36 and 38 are integrally connected together to form as a singlecomposite structure, display panel assembly 10. In the preferredembodiment, the overall thickness of this composite structure is lessthan 10 millimeters. Ultra-thin air gaps 32, 35, 37, 39 and 50 can beformed by very thin panel spacers realized as dimples formed inrespective panels or any other suitable techniques known in the art.

While PDLC material is used in the illustrative embodiment to form thelight diffusive structure of the present invention, it is understoodthat other suitable electro-optical structures, having switchable lightscattering and non-light scattering states of operation, may be used.

As shown in FIGS. 3 and 3A, a reflective layer 40 is applied to theinner surface of rear panel 21, which is hingedly connected to thecomputer display (or cover) portion. In the direct viewing mode,reflective layer 40 is disposed adjacent Fresnel lens panel 38 with anair gap 41 disposed therebetween, whereas reflective layer 40 and rearpanel 21 are removed away from display panel assembly 10 during theprojection viewing mode shown in FIGS. 5 and 5C.

In the first illustrative embodiment, light guiding structure 25 has athickness in the range of from about 1 to about 5 millimeters.Fluorescent lighting tubes 27 and 28 are driven by power supply 19 andsupported in miniature fixtures well known in the art. The lightingtubes are closely positioned along and in close proximity with opposingside edges of light guiding structure 25. Light rays emitted from theselighting tubes are focused by reflectors 28 and 29 along the side edgesof the light guiding structure, and effectively conducted into theinterior of the light guiding structure so that they are normallybounded (i.e. internally reflected) between light guiding surfaces 25Aand 25B in accordance with the well known optical principle of "totalinternal reflection".

Particularly during the direct viewing mode of operation, it isnecessary that the light trapped within the light guiding structure beuniformly extracted or "leaked out" in the direction of the LCD panel33. By doing so, only LCD panel 33 is allowed to spatially modulate (andspectrally filter) the light intensity distribution produced from thebacklighting panel and display color imagery. In accordance with thepresent invention, this function is performed byelectrically-controlling the first PDLC panel 25 (i.e. light guidingstructure) so that it interrupts the total internal reflection of thelight guided between the light guiding surfaces 25C and 25D of the lightguiding structure. In the illustrative embodiment, this function isrealized by coating the opposing interior surfaces 25E and 25F ofoptically transparent panels 25A and 25B with optically transparentelectrically-conductive layers 42 and 43 (e.g. Indium Tin Oxide) havingultra-thin dimensions (e.g. 1000 to 5000 Angstroms). As best shown inFIG. 3C, PDLC layer 26 is disposed between these electrically-conductivelayers. Importantly, specific optical materials are selected so thatoptically transparent panels 25A and 25B and cured polymer matrix 44therebetween (suspending liquid crystal molecules 45) have identicalindices of refraction.

As best shown in FIG. 3C, during the direct viewing mode, no externalelectric field (i.e. voltage) is applied across electrode surfaces 42and 43. Under such conditions, the electric field vectors ofpolymer-dispersed liquid crystals 45 between electrode surfaces 42 and42 are randomly oriented and light rays reflected between light guidingsurfaces 25C and 25D are scattered in accordance with the well knownLambertian distribution. Those scattered light rays no longer satisfyingthe critical angle for total internal reflection are transmitteddirectly through both light guiding surfaces 25C and 25D.

As shown in FIG. 5C, during the projection mode an external field (i.e.voltage) is applied across electrode surfaces 42 and 43, causing thePDLC molecules to align in the direction of the electric field,perpendicular to the light guiding surfaces 25C and 25D, and therebyeliminates light scattering. During this mode of operation, the PDLCpanel assumes its light non-scattering state so that the condition oftotal internal reflection is satisfied, with substantially no lightleaking from the light guiding structure. Only externally generatedlight rays, propagating substantially perpendicular to the light guidingsurfaces of the light guiding structure, are permitted to passcompletely through the backlighting panel onto LCD panel 33. To switchthe display system to its direct viewing mode, all that is required isto remove the voltage (i.e. external field) applied across electrodesurfaces 42 and 43, causing PDLC panel 26 to revert back to its lightscattering (i.e. diffusive) state of operation.

In order to ensure that the light leaked out through the front surfaceof the light guiding panel 25 is substantially uniform, it is necessaryto compensate for the inherent decrease in conducted light intensity inthe direction of the central axis of the light conductive panel. In theillustrative embodiments of the present invention, this compensationfunction can be achieved using any one of the techniques describedbelow.

A first method of light intensity compensation involves distributing theliquid crystal molecules within the PDLC 26 as a function of distanceacross the horizontal dimensions of the light guiding panel.Specifically, in the dual fluorescent tube configuration of the firstillustrative embodiment, the density of liquid crystals is made to begreater towards the center of the light guiding panel 25 where theintensity of conducted light is least. By doing so, compensation fordiminishing light intensity can be achieved. This technique can becarried out by preparing an emulsion of PDLC material formed frompolyvinyl acetate (PVA), polymethyl methacrylate (PMMA) or othersuitable polymer material, all well known in the art. Then liquidcrystal molecules are added to the emulsion. Using the prepared emulsionand screen printing techniques well known in the art, a pattern of PDLCemulsion material is formed on optically transparent electrode surface42 or 43. Notably, the geometry of the PDLC emulsion pattern will beselected with consideration to light intensity compensation across thebacklighting panel. Thereafter during PDLC film formation, microdropletsare formed spontaneously in the resulting PDLC film using a phaseseparation process. The phase separation can be induced bypolymerization, temperature, or a combination of solvent andtemperature. In particular, a phase-separation technique, such asPolymerization-Induced Phase Separation(PIPS), Thermally-Induced PhaseSeparation(TIPS) or Solvent-Induced Phase Separation can be used to formliquid crystal microdroplets dispersed in the PDLC film structure. ThePDLC film is fixed (i.e. cured) using UV radiation withphoto-initiators, both well known in the art. Finally, a layer of PVA orPMMA is applied over the fixed patterned PDLC film layer in order tofill-in the gaps between the pattern and form an optically smoothsurface.

When the light guiding structure 25 is completely fabricated, thereshould be complete index refraction matching from light guiding surface25C to light guiding surface 25D. While this optical condition must besatisfied to ensure optimal performance of the light guiding structure,it is understood that the choice of materials and fabrication techniquesused to realize this structure may vary from embodiment to embodiment.

A second method of light intensity compensation illustrated in FIGS. 3Dand 3E involves forming (i) primary and secondary sets of interleaved(optically-transparent) electrode strips 42A and 42B on the interiorlydisposed surface 25E of optically transparent panel 25A, and (ii) auniform optically transparent electrode surface 43 on the interiorlydisposed surface 25F of optically transparent panel 25B. As shown inFIGS. 3D and 3E, electrode strips 42A and 42B extend parallel to thevertical direction of light guiding structure 25. Electrode strips 42Aare electrically connected to a bus strip 42C, whereas electrode strips42B are electrically connected to bus strip 42D. As shown in FIG. 3D, anunpatterned uniform PDLC layer 26' is formed between these electrodesurface structures. In order to cause greater light scattering towardsthe central region of the light guiding structure and thus compensatefor light intensity in this region, the width of the interleavedelectrode strips 42A and 42B increases a towards the center of the lightguiding structure, as shown. In general, the width of the gap betweenadjacent electrode strips is substantially smaller than the width of theelectrode strips. This ensures that during the projection viewing mode,when an external electric field is applied across both the primary andsecondary sets of electrode strips and all liquid crystal moleculesalign therewith and pose no light scattering in this state of operationperturbations in the electric field intensity is negligible at thefringe areas of the electrode surfaces. Also, the thickness of the PDLClayer 26 is made substantially smaller than the width of the narrowestelectric strip to ensure that the electric field between the electrodestrip and the ground electrode surface is substantially uniform.

In the direct viewing mode, it is essential that light internallyreflected between light guiding surfaces 25C and 25D is permitted toescape or leak out towards LCD panel 33. During the direct viewing mode,internally reflected light is permitted to escape light guidingstructure by applying an external field only across the secondary set ofelectrode strips 42B. In response, the electric field vectors of theliquid crystal molecules below the secondary set of electrode strips42B, are randomly oriented and a pattern of non-scattering liquidcrystal molecules are formed. Between the primary set of electrodestrips 42A and the uniform electrode surface 43, across which noelectric field is applied, the electric field vectors of the liquidcrystal molecules are randomly oriented and light scattering occurs.Naturally, during the direct viewing mode, a greater degree of lightscattering occurs under the wider electrode strips of the primary set ofelectrodes 42A, than under the narrower electrode strips in the primaryset. Collectively, the resulting light scattering pattern so formedprovides the degree of light intensity compensation required for highquality imaging through LCD panel 33.

A third method of light intensity compensation is illustrated in thedrawings of FIGS. 3F to 3H. As shown in FIG. 3F, the first step of themethod involves providing a uniform layer of PDLC film 26' between apair of unpatterned optically transparent electrode layers 42 and 43.Typically, each optically transparent electrode layer is formed from amaterial such as Indium Tin Oxide. Preferably, PDLC film layer 26'consists of a distribution of encapsulated liquid crystal microdroplets(i.e. "liquid crystal microdroplets") with diameters of about 0.1 toabout 10 microns, surrounded by or uniformly dispersed in a lighttransmissive matrix of photo-sensitive polymer, such as Norland 65Photopolymer, commercially available from Norland, Inc., of New Jersey.

At this stage of the manufacturing process, a suitable emulsion for thePDLC film must be prepared. In the illustrative embodiment, the firststep in preparing the emulsion involves forming a homogeneous, fairlyviscous solution formed by intermixing nematic, smectic or cholestericliquid crystal molecules with appropriate liquid polymer precursors(e.g. prepolymer or monomer) and curing agent, such as liquid UVphoto-initiator. Suitable materials for use in preparing the homogeneoussolution are well known to those with ordinary skill in the art. Alsowell known details regarding PDLC film manufacture are disclosed in thepaper "Polymer-Dispersed and Encapsulated Liquid Crystal Films" by G.Paul Montgomery, Jr., published in Large-Area Chromogenics: Materialsand Devices for Transmittance Control, SPIE Institute Series Vol. IS 4,pages 577-606, incorporated herein by reference in its entirety. Onceprepared, the viscous solution can be applied between a pair ofsubstrates coated with optically transparent conducting electrode layers42 and 43, to form a film emulsion structure of the required thickness.Typically, Indium Tin Oxide(ITO) is used to form optically transparentelectrode layers 42 and 43.

In general, microdroplets in the PDLC film emulsion structure are formedspontaneously by a phase separation process which occurs during filmformation. The phase separation can be induced by polymerization,temperature, or a combination of solvent and temperature. In particular,a phase-separation technique, such as Polymerization-Induced PhaseSeparation(PIPS), Thermally-Induced Phase Separation(TIPS) orSolvent-Induced Phase Separation can be used to form liquid crystalmicrodroplets dispersed in the PDLC film structure.

In the illustrative embodiment, the liquid phase encapsulated withineach liquid crystal microdroplet generally comprises: (i) a largepercentage of liquid crystal molecules (e.g. about 99% by volume); (ii)a very small percentage of liquid prepolymer or monomer (e.g. less than1.0% by volume); and (ii) a very small percentage of curing agent, suchas liquid photo-initiator (e.g. less than 1.0% by volume). While theencapsulated liquid crystals may be of the nematic, smectic orcholesteric type, nematic liquid crystals are the preferred lightscattering medium in the illustrative embodiments. Upon completing thisstage of the manufacturing process, the substrates are removed toprovide a PDLC film structure having a thin layer of PDLC filmsandwiched between optically transparent, conducting electrode layers 42and 43. The length and width dimensions of the resulting PDLC filmstructure may be large or small depending upon the commercialapplication.

As shown in FIG. 3G, the second step of the method involves exposing theentire PDLC film structure to a pattern of ultra-violet(UV) lightprojected using spatial mask 140 and UV light projector 141, while a"reference" electric field, directed substantially perpendicular to theplane of the PDLC film structure, is applied across opticallytransparent electrode layers 42 and 43 in order to align the opticalaxis of each liquid crystal microdroplet parallel therewith. Preferably,the pattern of light transmission apertures 140A in spatial mask 140 issubstantially similar to the electrode pattern shown in FIG. 3D. Duringthis stage of the manufacturing process, several chemical reactionsoccur. Firstly, those portions of the photo-sensitive polymer matrix(i.e. PDLC film structure) that have been exposed to the UV lightpattern become cured. Secondly, the monomer material in the liquidcrystal microdroplets that have been exposed to the UV light patternbecomes polymerized in the presence of the photo-initiator and UV light,thereby forming a polymer network in each such liquid crystalmicrodroplet. The function of the polymer network within eachmicrodroplet is to physically entrap the liquid crystal moleculestherewithin so that the optical axis of the microdroplet is elasticallybiased or aligned parallel to the direction of the reference electricfield (i.e. perpendicular to the plane of PDLC film layer). During thisstage of the manufacturing process, the regions of the PDLC filmstructure that are blocked by the spatial mask, do not cure in theabsence of UV light. The result of this step of the manufacturingprocess is the formation of a first pattern of polymer-dispersed liquidcrystal microdroplets whose optical axes are elastically biased in adirection perpendicular to the plane of the PDLC film structure.

As shown in FIG. 3H, the third step of the method involves firstremoving the reference electric field from across the electrode layers42 and 43. In the absence of an external electric field, the opticalaxes of the microdroplets blocked from the UV light pattern during theprevious stage, are now permitted to orient their respective opticalaxes in a random manner within the photo-sensitive polymer matrix. Then,the entire PDLC film structure is exposed to ultra-violet(UV) lightusing the UV light projector 141 (without spatial mask 140), while the"reference" electric field is removed from across electrode layers 42and 43. During this stage of the manufacturing process, severalphoto-chemical reactions occur. Firstly, the remainder of thephoto-sensitive polymer matrix is cured. Secondly, monomer material inmicrodroplets with randomly oriented optical axes, becomes polymerizedin the presence of the photo-initiator and UV light, thereby forming apolymer (i.e. polydomain) network in each such microdroplet. Thefunction of the polymer network within each such microdroplet is tophysically entrap the liquid crystal molecules therewithin so that theoptical axis of each microdroplet is elastically biased in a randomorientation.

The resulting structure is a PDLC panel having a first pattern ofpolymer-dispersed liquid crystal microdroplets whose optical axes areelastically biased in a direction perpendicular to the plane of the PDLCpanel, and a second pattern of polymer-dispersed liquid crystalmicrodroplets whose optical axes are elastically biased in directionsthat are random with respect to the plane of the PDLC panel.

When there is no external electric field applied across the electrodelayers 42 and 43 of the PDLC panel, the randomly oriented optical axesof the second pattern of liquid crystal microdroplets provide the "lightscattering (i.e. diffusing) state" of operation required to extractlight from the backlighting panel during the direct viewing mode. At thesame time, the second pattern of liquid crystal microdroplets in PDLCpanel 26' achieves the desired degree of intensity compensation requiredin the light panel.

When an external electric force field is applied across the electrodelayers 42 and 43 in a direction perpendicular to the plane of the PDLCpanel, the optical axes of second pattern of liquid crystalmicrodroplets are forcefully reoriented away from their randomdirections and aligned parallel to the direction of the elasticallybiased optical axes of the first pattern of liquid crystalmicrodroplets. This provides the "light non-scattering state" ofoperation required for non-diffusive passage of projected light duringthe projection viewing mode.

For the remainder of the description of the present invention, it shallbe assumed for exposition purposes only that light intensitycompensation in light guiding structure 25 is achieved using a patternedPDLC layer 26 and electrode surfaces 42 and 43, as shown in FIGS. 3A and5B and described above. It is understood, however, that the descriptiongenerally applies when PDLC layers 26', 26" or any other functionallyequivalent structure is used for selectively controlling light diffusionin the light panel of the present invention.

In the direct viewing mode of operation, when no applied electric fieldis applied across electrodes 42 and 43 of the first PDLC panel, theliquid crystal molecules dispersed therein are randomly oriented.Consequently, the light conducted within light guiding structure 25 isscattered the most along the central portion thereof. The result is asubstantially uniform light intensity distribution emanating from lightguiding structure 25 in the direction of LCD panel 33, as well as in thedirection of PDLC panel 31.

To ensure that only LCD panel 33 of the display panel assembly imparts aspatial intensity modulation to the light distribution emanating fromthe display surface towards the viewer's eyes, it is essential the lightintensity behind LCD panel 33 be highly uniform along the x and ycoordinates of the display panel assembly. The function of the PDLCpanel 31 is to further ensure that this condition is satisfied byuniformly diffusing (i.e. scattering) light passing through lightguiding surface 25D. In the illustrative embodiment, this lightdiffusion function is achieved by constructing the PDLC panel 31 in amanner similar to that of the first PDLC panel (i.e. light guidingstructure 25). Specifically, opposing interior surfaces 31E and 31F ofoptically transparent panels 31A and 31B are coated with opticallytransparent electrically-conductive layers 46 and 47 (e.g., Indium TinOxide ITO) having ultra-thin dimensions (e.g. 1000 to 5000 angstroms).As shown, PDLC layer 31G is disposed between these electricallyconductive electrode surfaces. In the PDLC panel 31, the distribution(i.e. density) of liquid crystal molecules is substantially uniformacross the horizontal dimensions of the panel. The index or refractionof optically transparent panels 31A and 31B and the cured polymer matrix(supporting liquid crystal molecules) therebetween are substantiallyidentical. In the direct viewing mode, when no external electric fieldis applied across electrode surfaces 46 and 47, the electric fieldvectors of the polymer-dispersed liquid crystals between these electrodesurfaces are randomly oriented and light rays emerging from lightguiding structure 25 and passing through the PDLC panel 31 are uniformlyscattered in accordance with the well known Lambertian distribution. Theresult is a highly uniform light intensity distribution emerging fromthe PDLC panel 31 in the direction of PDLC panel 34. In the projectionviewing mode, when an external electric field (i.e. voltage) is appliedacross electrode surfaces 46 and 47, the electric field vectors of thepolymer-dispersed liquid crystals between these electrode surfaces alignwith the applied electric field, to yield the light non-scattering stateof operation. In this switched optical state, light rays projectedperpendicularly through light guiding structure 25 from an externallight projector, pass through PDLC panel 31 without scattering, asrequired to illuminate LCD panel 33 during the projection viewing modeof the display subsystem of the present invention.

In display panel assembly 10, the function of the PDLC panel 34 issimilar to the function of PDLC panel 31, described above. Specifically,during the direct viewing mode, the function of PDLC panel 34 is tofurther diffuse (i.e. scatter) light emerging from PDLC panel 31. In theillustrative embodiment, this light diffusion function is achieved byconstructing the PDLC panel 34 in a manner identical to that of the PDLCpanel 31. Specifically, opposing interior surfaces 34E and 34F ofoptically transparent panels 34A and 34B are coated with opticallytransparent electrically-conductive layers 48 and 49 (e.g. Indium TinOxide ITO) having ultra-thin dimensions (e.g. 1000 to 5000 Angstroms).As shown, PDLC layer 34G is disposed between these electricallyconductive electrode surfaces. In the PDLC panel 34, the distribution(i.e. density) of liquid crystal molecules is substantially uniformacross the horizontal dimensions of the panel. The index or refractionof optically transparent panels 34A and 34B and the cured polymer matrix(supporting liquid crystal molecules) therebetween are substantiallyidentical. In the direct viewing mode, when no external electric fieldis applied across electrode surfaces 48 and 49, the electric fieldvectors of the polymer-dispersed liquid crystals between these electrodesurfaces are randomly oriented and light rays emerging from PDLC panel31 and passing through the PDLC panel 34 are uniformly scattered inaccordance with the well known Lambertian distribution. The result is avery-highly uniform light intensity distribution emerging from the PDLCpanel 34 in the direction of LCD panel 33.

In the direct viewing mode, light scattering within the light guidingstructure 25 generally occurs in accordance with the well knownLambertian distribution. The scattered light rays propagating in thedirection of reflective surface 40 first passes through PDLC panel 36and Fresnel lens panel 38, reflects off reflective surface 40 and thenpasses through Fresnel lens panel 38, PDLC panel 36 and light guidingstructure 25 prior to passing through PDLC panels 31 and 34 andultimately onto LCD panel 33. During the direct viewing mode, PDLC panel36 functions to diffuse this scattered/reflected light as it propagatesthrough light transmission surfaces 36C and 36D of PDLC panel 36. Thislight diffusion function is achieved by constructing the PDLC panel 36in a manner similar to that of the PDLC panels 30, 31 and 34.Specifically, opposing interior surfaces 36E and 36F of opticallytransparent panels 36A and 36B are coated with optically transparentelectrically-conductive layers 51 and 52 (e.g., Indium Tin Oxide ITO)having ultra-thin dimensions (e.g. 1000 to 5000 Angstroms). As shown,PDLC layer 36G is disposed between these electrically conductiveelectrode surfaces. In the PDLC panel 36, the distribution (i.e.density) of liquid crystal molecules is substantially uniform across thehorizontal dimensions of the panel. The index of refraction of opticallytransparent panels 36A and 36B and the cured polymer matrix (supportingliquid crystal molecules) therebetween are substantially identical. Inthe direct viewing mode, when no external electric field is appliedacross electrode surfaces 51 and 52, the electric field vectors of thepolymer-dispersed liquid crystals between these electrode surfaces arerandomly oriented and light rays reflecting off reflective surface 40,and passing through PDLC panel 36 are uniformly scattered in accordancewith the well known Lambertian distribution. The result is a highlyuniform light distribution emanating from PDLC panel 36 in the directionof light guiding structure 25.

In the direct viewing mode, the collective function of light guidingstructure 25 and electronically-controlled light diffusing panels 31,34, and 36 is to produce a plane of backlighting having a highly uniformlight intensity characteristics along the x and y coordinate directionsof LCD panel 33. In order to display imagery of one sort or another fromthe computer system, LCD panel 33 spatially modulates the intensity ofthe plane of uniform backlighting as it propagates through the LCDpanel.

In the illustrative embodiments, LCD panel 33 comprises a programmablespatial color mask (i.e. spatial spectral mask) disposed over aprogrammable spatial light intensity mask (i.e. spatial light modulatoror SLM). In general, the programmable spatial light mask comprises afirst array (i.e. matrix) of electrically addressable pixels, and theprogrammable spatial color mask comprises a second array of electricallyaddressable pixels.

In a manner well known in the art, each pixel in the programmablespatial light mask is formed from a material having a lighttransmittance (over the optical band) which can varied in accordancewith pixel intensity information to be displayed. In a conventionalmanner, each pixel in this spatial light mask is driven by pixel drivercircuitry 11 operated under the control of display controller 13. Thedegree to which the light transmittance of each pixel in the array ismodulated, is determined by the gray-scale or intensity informationcontained in the corresponding pixel location in frame buffer 12. Thegray scale information of a particular image to be displayed is writtenin frame buffer 12 by display processor 13, and is scanned and convertedinto pixel drive signals by the pixel driver circuitry 11.

When color images are to be displayed, the programmable spatial color(i.e. spectral) mask is actively driven by pixel driver circuitry 11.Each pixel in the programmable spatial color mask has spectraltransmittance characteristics which can varied in accordance with colorinformation to be displayed. In a conventional manner, each of thepixels in the programmable spatial color mask is driven by designateddriver lines of X and Y pixel drivers 11. The spectral transmittancecharacteristics of each pixel in the array are determined by the pixelcolor information in frame buffer 12.

Having described the first illustrative embodiment of the display panelassembly of the present invention, it is appropriate to describe thesecond illustrative embodiment thereof designated by reference numeral10'.

As shown in FIGS. 3 and 3B in particular, the display panel assembly 10'comprises a novel electro-optical light panel construction integratedwith a conventional LCD display panel. The electro-optical light panelconstruction comprises a number of integrated components, namely: anoptically transparent light guiding panel 25'; fluorescent lightingtubes 27 and 28; elongated concave light reflectors 29 and 30;electrically-controlled PDLC panel 31 directly laminated onto frontsurface 25B' of light guiding panel 25'; electrically-controlled PDLCpanel 34 affixed to the front surface of electrically-controlled PDLCpanel 31 with an ultra-thin air gap 35 disposed therebetween;electrically-controlled PDLC panel 36 affixed to rear surface 25A' oflight guiding panel 25' with an ultra-thin air gap 37 therebetween; andFresnel lens zone structure formed in a thin optically transparent layer38 affixed to the rear surface of electrically-controlled PDLC panel 36with ultra-thin air gap 39 disposed therebetween. Together, panels25',31,34,36 and 38 form the electro-optical light panel of compositeconstruction. In the illustrative embodiment, active-matrix LCD displaypanel 33 is affixed to the front surface of the electrically-controlledPDLC panel 34 with ultra-thin air gap 50 disposed therebetween. As such,panels 25', 31,33, 34, 36 and 38 are integrally connected to form as asingle composite structure, display panel assembly 10'. In the preferredembodiment, the overall thickness of this composite structure is lessthan 10 millimeters.

As shown in FIGS. 3 and 3B, reflective layer 40 is applied to the innersurface of rear panel 21 in substantially the same manner provided inthe first illustrative embodiment of the display panel assembly. In thedirect viewing mode, reflective layer 40 is disposed adjacent Fresnellens panel 38, whereas reflective layer 40 and rear panel 21 are removedaway from the light panel hereof in the projection viewing mode shown inFIGS. 5 to 5B.

In display panel assembly 10', light guiding panel 25' is in the form ofsolid sheet of material (e.g. PVA or PMMA) having the same index ofrefraction as optically transparent panels 31A and 31B, and the polymermatrix of PDLC layer 31G disposed therebetween. Preferably, thethickness of light guiding panel 25' is in the range of from about 1 toabout 5 millimeters. Electrically controlled PDLC panel 31 isconstructed as described above in connection with display panel assembly10. When light guiding panel 25' and optically transparent panel 31A aresecured together by a suitable adhesive, the index of refraction isconstant (i.e. substantially the same) from light guiding surface 25A'to light transmission surface 31D of PDLC panel 31.

In display panel assembly 10', fluorescent lighting tubes 27 and 28 aredriven by power supply 19 and supported in miniature fixtures attachedto the side edges of light guiding panel 25'. The fluorescent tubes areclosely positioned along and in close proximity with opposing side edgesof light guiding panel 25' so that emitted light from the tubes isfocused by reflectors 29 and 30 along the side edges of the lightguiding panel and effectively conducted into the interior of lightguiding panel 25'. In all other respects, display panel assembly 10' isconstructed in a manner similar to display panel assembly 10.

In the direct viewing mode of operation, when no applied electric fieldis applied across electrodes 46 and 47 of PDLC panel 31, the liquidcrystal molecules dispersed therein are randomly oriented. Consequently,the conducted light within the light guiding panel 25' is scattered themost along the central portion of PDLC panel 31, with a substantiallyuniform light intensity distribution emanating from PDLC panel 31 in thedirection of PDLC panel 34. In the direct viewing mode, PDLC panels 34and 36, Fresnel lens panel 38, reflective layer 40, and LCD panel 33 ofdisplay panel assembly 10' operate and function in the same manner indisplay panel assembly 10. In the projection viewing mode, PDLC panels34 and 36, and LCD panel 33 of display panel assembly 10' operate andfunction in the same manner in display panel assembly 10.

Computer-based system 1 of the illustrative embodiment has two directviewing modes of operation, namely: An Illuminated Direct Viewing Modefor directly viewing images displayed on LCD panel 33; and AnIlluminated Direct Backlighting Mode for directly viewing opticallytranslucent film structures, such as slides and optical transparencies.Both of these direct viewing modes will be described below.

Portable computer system 1 is operated in its Illuminated Direct ViewingMode of operation by performing the following simple operations: (i)moving rear panel 21 and reflective surface 40 against Fresnel lenspanel 38 of display panel assembly 10; (ii) electronically reconfiguringdisplay panel assembly 10 into its direct viewing state of operation bynot applying an electric field across the optically transparentelectrodes of the PDLC panels 25, 31, 34 and 36; and (iii) then drivingfluorescent tubes 27 and 28 in order to inject light into light guidingpanel 25, while driving LCD panel 33 with pixel drive signals derivedfrom the image data set written into frame buffer 12. However, incertain circumstances it might be desirable to operate the computersystem in an alternative direct viewing mode, in which the fluorescenttubes 27 and 28 and light diffusing panels 25, 31, 34 and 36 are notdriven, and backlighting is provided solely by ambient light passingthrough the display panel assembly 10 and reflecting off reflectivelayer 40 in the direction of the viewer of LCD panel 33. Thisalternative mode of direct viewing is referred to as the DirectReflection Viewing Mode of operation and is particularly useful when theintensity of ambient light is high, as in outdoor environments, and whenelectrical power reserves in the portable computer are limited.

Preferably, portable computer system 1 is operated in its IlluminatedDirect Backlighting Mode of operation by performing the following simpleoperations: (i) moving rear panel 21 and reflective surface 40 againstFresnel lens panel 38 of display panel assembly 10; (ii) electronicallyreconfiguring display panel assembly 10 into its direct viewing state ofoperation by not applying an electric field across the opticallytransparent electrodes of the PDLC panels 25, 31, 34 and 36; and (iii)then driving fluorescent tubes 27 and 28 in order to inject light intolight guiding panel 25, while not driving LCD panel 33 with pixel drivesignals.

The structure and function of display panel assemblies 10 and 10' havebeen described above in great detail. It is appropriate at this junctureto now describe the portable light projection device of the presentinvention.

As shown in FIGS. 6A to 8, portable light projection device 60 of thepresent invention comprises a number of structural components, namely:first and second housing portions 61 and 62; and foldable structure 63.As shown in its compact storage configuration in FIG. 6A, first andsecond housing portions 61 and 62 are releasably joined at their ends ina snap-fit manner. As shown in its partially extended configuration inFIG. 6B, the first and second housing portions are shown interconnectedby foldable structure 63. In the illustrative embodiment, first andsecond housing portions 61 and 62 each have a cubical geometry, whilefoldable structure 63 is realized as a plurality of hingedly connectedpanels 63A to 63E. As shown, each panel is hinged to at least one otherpanel, and one panel is hinged to the bottom of the first housingportion, and another panel is hinged to the bottom of second housingportion. These panels can be folded upon each other in sequence, andthen the upper rim 65 of first housing portion connected to the uppergroove 66 formed in the second housing portion, as shown in FIG. 6A.When the portable light projection device is needed for the projectionviewing mode, the first and second housing portions can be separated andthe panels unfolded so that the housing portions are separated by adistance substantially equal to the width of the base of the computersystem, as shown in FIG. 4A.

As shown in FIG. 7, first housing portion 61 contains electrical powercircuitry 70 for transforming standard household AC power (60 Hz),supplied over electrical wiring 71, to a sufficient level of DC power.Mounted above this circuitry is an electrical socket 72 within which ismounted an incandescent lamp 73. About the lamp is a parabolic lightfocusing reflector 74. Electrical socket 72 and an ON/OFF switch 75externally mounted through the side wall of the first housing portionare connected to electrical power circuitry 70. An internal fan unit 76is connected to electrical power circuitry 70 for maintaining thetemperature of the lamp at a safe operating level. Mounted above thelight focusing reflector 74 is a polarizing filter panel 77 whichpolarizes the light produced from lamp. Preferably, polarization filter77 is manufactured from cholesteric liquid crystal (CLC) material, asdisclosed in U.S. Pat. No. 5,221,982 to Applicant, which is incorporatedby reference in their entirety. While polarizing filter 77 is shown inthe form of a panel, the function which it achieves can be realized in amaterial applied as a coating over a high-intensity light bulb, such asincadescent lamp 73. Significantly, the installation of polarizingfilter 77 in the portable light projection device avoids dissipating thepower of the undesired polarization component across LCD panel 33 of theLCD panel assembly. Consequently, display panel assembly 10 (and 10') ispermitted to operate a lower temperatures without need for cooling ordisplay-panel temperature measures in the portable computer system whenoperated in its projection viewing mode.

Above the light polarizing panel 77, and below light aperture 68 inhousing 61, is an adjustable optics assembly 78 for focusing producedpolarized light on the interior surface of the rear panel. Opticsassembly 78 includes a lens system mounted in housing portion 61 in aconventional manner. Preferably, slidable lens mounts are used tosupport the lenses of this system in a manner that permits adjust of thefocal length thereof by rotation of knob 69, external to housing portion61.

As shown in FIGS. 6B and 8, the second housing portion contains anoptical platform 80 a lens holder 81, light projection lens 82, andfirst and second platform support sleeves 83 and 84. As shown in FIG.4A, platform 80 is mounted upon the top portion of platform support 82,whereas platform support sleeves 83 and 84 are telescopicallyinterconnected and joined to the cubic shaped second housing portion 62.As shown in FIGS. 4A and 6B, lens holder 81 is slidably mounted withingrooves 85 and 86 formed in optical platform 80 such that the positionof lens holder 81 along the optical platform can be easily adjusted bysimply rotating a knob 87. In the preferred embodiment, knob 87 isoperably associated with a platform translation mechanism 88 containedbeneath optical platform 80 itself. Within lens 81, image projectionlens 82 is securely mounted. With the above described arrangement, imageprojection lens 82 can be adjustably positioned with respect to LCDpanel 33 in order to project a focused video image onto a desiredviewing surface.

A method of using portable light projection device 60 with portablecomputer system 1 will be described below. However, as display panelassemblies 10 and 10' have similar modes of operation, the followingdescription shall be made with reference to portable computer system 1incorporating display panel assembly 10 into its image displaysubsystem.

In FIGS. 4 and 4A, portable computer system 1 is shown arranged in itsfirst projection viewing configuration using portable light projectiondevice 60 of the present invention. The first projection viewingconfiguration is achieved by arranging the portable light projectingdevice in its extended configuration, about base 2 of the computersystem, as shown. Hinged rear housing panel 21 is pulled outwardly awayfrom Fresnel lens panel 38 so that light reflective surface 40 issupported at about a 45 degree position with respect to the Fresnel lenspanel by a conventional support mechanism 21A, as shown in FIG. 4A. Inprojection viewing configuration, the first housing portion 61 of theportable light projecting device is disposed below the reflectivesurface, while an image projection lens 62 extends from the secondhousing portion 63.

Once configured as shown in FIG. 4A, portable light projection device 60is adjusted as follows. First, the lateral position of first housingsection 61 is adjusted so that the optical axis of projection lens 78 inthe first housing portion is aligned under reflective surface 40. Lensholder 81 is then pulled upwardly out of the frictional embrace of thesecond platform support sleeve 84, as shown in FIG. 6B. Then by pullingfurther upwardly, the second platform support sleeve 84 slides out ofthe frictional embrace of the first platform support sleeve 83 and thenwhen further pulled upwardly, the first platform support sleeve slidesout of the frictional embrace of the cubic shaped second housingportion, as shown in FIG. 4 A. Then, with power supplied to light source73 and light emitting therefrom, the position of projection lens 82along the optical axis of Fresnel lens panel 38 is adjusted so that theimages formed on the display surface of LCD panel 33 are projected asenlarged focused images onto large viewing surface 89. In general,projection lens 82 is positioned in front of the display panel assemblyat a distance equal to the focal length of Fresnel lens panel 38.

When it is desired to arrange portable light projecting device 60 backinto its compact storage configuration, as shown in FIG. 6, lens holder81 is simply pushed downwardly, to collapse platform support sleeves 83and 84 in a manner opposite to the telescopic extension processdescribed above. Thereafter, hingedly connected panels 63A to 63E arefolded upon each other and finally first housing portion 61 is snap-fitconnected to second housing portion 62, to provide a singleinterconnected unit of physical dimensions of 3"×3"×6", as shown in FIG.6A

The geometrical optics that describe the image projection process aregraphically illustrated in FIG. 4A. Specifically, during the projectionviewing mode, the light rays produced from light source 73 in the firsthousing portion are first polarized by polarizer 77, and then focused ina divergent manner onto reflective surface 40 by projection lens 78. Thepolarized light rays are then reflected off reflective surface 40,passed through backlighting construction of display panel assembly 10with minimal attenuation and ultimately passed through and opticallyprocessed by LCD panel 33. The light rays emanating from actively drivenLCD panel 33 are spatial intensity modulated and spectrally filtered inaccordance with the X,Y drive signals provided to pixel driver circuitry11, and are then focused by projection lens 82 to produce a focusedvideo image on viewing surface 89, which is typically located at thefocal distance of projection lens 82. The structural details of thedisplay panel assembly in the projection viewing configuration are shownin FIGS. 5 to 5A.

In FIG. 4B, portable computer system 1 is shown arranged in its secondprojection viewing configuration using an alternative embodiment ofportable light projection device 60 of the present invention, indicatedby reference numeral 60'. All some respects, first housing portion 61'of light projection device 60' is different from that of lightprojection device 60 shown in FIG. 4A. In particular, the polarizedlight source contained in the first housing portion of light projectiondevice 60' is telescopically extendable to the height of projection axis200, and is ported on its side, as shown, to permit direct projection offocused polarized light towards the light panel assembly 10 with itsintegrated Fresnel lens panel. In all respects, the second housingportion 62 of light projection device 60' is the same as the secondhousing portion of light projection device 60 shown in FIG. 4A. Duringtransport, both the first and second housing portions are collapsableand then configurable as described in connection with light projectiondevice 60 above.

As shown in FIG. 4B, the second projection viewing configuration isachieved by arranging the portable light projecting device 60' in itsextended configuration, about the base of the computer system. Hingedrear housing panel 21 is pulled outwardly away from Fresnel lens panel38 so that light reflective surface 40 is supported at about a 65 degreeposition with respect to the Fresnel lens panel by a conventionalsupport mechanism 21A, as shown in FIG. 4B. In the second projectionviewing configuration, the first housing portion 61' of the portablelight projecting device 60' is disposed below the reflective surface andalong the optical projection axis 200 of the Fresnel lens panel, whilean image projection lens 82 is telescopically extended from the secondhousing portion 62 and is aligned along the optical projection axis, asshown. In this alternative embodiment, first housing portion 61'includes a polarized light source 73, 77 of the type disclosed in FIG.7, which projects a diverging yet focused beam of polarized lightdirectly through the display panel 10, without the need to reflect offthe reflective surface 40 on the hinged display panel cover. In fact, inthis second projection configuration, it is possible to remove thedisplay panel cover 21 if desired. During operation, polarized lightfrom the light projection device 60' is projected through the displaypanel 10 while it is being operated in its projection mode and videosignals are driving the pixels thereof. The polarized light rays passingthrough the display panel are spatial intensity modulated, andthereafter focused by image projection lens 82 onto a projection displaysurface (e.g. wall surface) remotely situated from the computer system,as shown in FIG. 4B.

In the alternative portable light projection device 60' shown in FIG.4B, the first housing portion 61' may be adapted to contain a number ofelectronic components and circuitry, namely: a pair of small audiospeakers with amplification circuitry; power supply circuitry for thepolarized light source; input signal ports for receiving audio signalsfrom the computer system; and output signal ports for transmittingcontrol signals back to the computer system in order to control theoperation of the computer system during video presentations. Addition, aPCMCIA port may also be provided within the first housing portion 61'for receiving a PCMCIA-based infrared transceiver card adapted fortransmitting and receiving IR-control signals between itself and aremote control device in order to control the operation of the computersystem in a remote fashion in manner well known in the art.

Advantageously, portable computer system 1 has two different projectionviewing modes, namely: a Projection Viewing Mode and an EnhancedProjection Viewing Mode. Notably, selection of either of these modes ofimage viewing is achieved without having to disassemble or mechanicallyreconfigure the display panel assembly of the present invention.

Computer system 1 can be operated in its Projection Viewing Mode byperforming the following simple operations: (i) moving rear panel 21 andreflective surface 40 away from Fresnel lens panel 38 of display panelassembly 10; (ii) electronically reconfiguring display panel assembly 10into its projection viewing state of operation by applying an electricfield across the optically transparent electrode surfaces of PDLC panels25, 31, 34 and 36; and (iii) then projecting an external source of lighttherethrough while driving LCD panel 33 with X,Y pixel drive signalsderived from the image data set written into frame buffer 12. Notablyduring this mode of operation, fluorescent tubes 27 and 28 are notsupplied with electrical power and light from portable light projectingdevice 60 is used to provide backlighting for LCD panel 33, as describedabove.

Computer system 1 can be operated in its Enhanced Projection ViewingMode by performing the following simple operations: (i) moving rearpanel 21 and reflective surface 40 away from Fresnel lens panel 38 ofthe display panel assembly; (ii) electronically reconfiguring thedisplay panel assembly into its projection viewing state of operation byapplying an electric field across the optically transparent electrodesurfaces of PDLC panels 25, 31, 34 and 36; (iii) supplying electricalpower from supply 19 to fluorescent tubes 27 and 28; and (iv) thenprojecting an external source of preferably polarized light therethroughwhile driving LCD panel 33 with pixel drive signals derived from theimage data set written into frame buffer 12.

In either of the above-described projection viewing modes, power supply19 is used to apply an electric field across the optically transparentelectrode surfaces of PDLC panels 25, 31, 34 and 36. In the illustrativeembodiment, the electric field strength applied across each of thesepanels is in the range of about 2 to about 20 Volts/micron. In each ofthese projection viewing modes, the electric field vectors of thedispersed liquid crystal molecules become physically aligned in thedirection of the externally applied electric field, as illustrated inFIG. 5C. In this optical state, light passes through these physicallyaligned liquid crystal molecules without scattering, and is ultimatelyintensity and spectrally modulated by LCD panel 33, on a pixel by pixelbasis.

Referring now to FIGS. 9 to 11A, the second illustrative embodiment ofthe present invention is realized in the form of a portable computersystem 1' capable of displaying spatially multiplexed images of 3-Dobjects for stereoscopic viewing thereof. In the illustrativeembodiment, computer system 1' has the general system architecture shownin FIG. 2. In FIG. 9, computer system 1' is shown arranged in the directviewing configuration. In FIGS. 10 and 10A, computer system 1' is shownarranged in its projection viewing configuration using a conventionaloverhead projector 90. Display panel assembly 10" of the thirdillustrative embodiment is shown in FIGS. 11 and 11A, whereas displaypanel assembly 10'" of the fourth illustrative embodiment is shown inFIGS. 11 and 11B.

As can be seen from FIGS. 11 and 11A, display panel assembly 10" isidentical to display panel assembly 10 of the first embodiment, and thedisplay panel assembly 10" is identical to display panel assembly 10'",with several modifications. In particular, a micropolarization panel 110is directly laminated onto the front surface of LCD panel 33, and thereis no Fresnel lens panel 36 affixed to PDLC panel 36. Notably, however,Fresnel lens panel 38 may be retained as in the first illustrativeembodiment of the present invention. In addition, rear panel 21' incomputer system 1' is adapted for simple removal during the projectionviewing mode, as shown in FIG. 9.

In portable computer system 1', the function of LCD panel 33 is todisplay "spatially multiplexed images (SMI)" of a 3-D object forstereoscopic viewing through a pair of polarized glasses 111 worn byviewers thereof. In general, each spatially-multiplexed image displayedfrom either display panel assembly 10" or 10'" is a composite pixelpattern composed of first and second spatially modulated perspectiveimages of the 3-D object. The first spatially modulated perspectiveimage consists of a first pixel pattern that is representative of afirst perspective image of the object and spatially modulated accordingto a first spatial modulation pattern. The second spatially modulatedperspective image consisting of a second pixel pattern that isrepresentative of a second perspective image of the object and spatiallymodulated according to a second spatial modulation pattern. The secondspatial modulation pattern is the logical complement of the firstspatial modulation pattern.

As best shown in FIGS. 11 and 11A, each spatially-multiplexed imagedisplayed from LCD panel 33 is optically processed by micropolarizationpanel 110. In the illustrative embodiment, micropolarization panel 110is realized as a optically transparent sheet directly mounted onto thedisplay surface of LCD panel 33. Permanently formed within the opticallytransparent sheet are first and second optically transparent patterns.The first optically transparent pattern spatially corresponds to and isspatially aligned with the first pixel pattern in the displayedspatially-multiplexed image. The function of the first opticallytransparent pattern is to impart a first polarization state P₁ to theradiant energy (i.e. light) associated with the first pixel pattern. Thesecond optically transparent pattern spatially corresponds to and isspatially aligned with the second pixel pattern in the displayedspatially-multiplexed image. The function of the second opticallytransparent pattern is to impart a second polarization state P₂ to theradiant energy (i.e. light) associated with the second pixel pattern.Importantly, the second polarization state P₂ is different than thefirst polarization state P₁ so that encoded perspective images aresimultaneously displayed from polarization panel 110 with opticallydifferent polarization states. To ensure high spatial separation betweenthe displayed perspective images, the first and second opticallytransparent patterns each have a spatial period of less than about 50microns.

Details regarding the manufacture of micropolarization panel 110 aredisclosed in copending U.S. application Ser. No. 07/536,419 entitled"Methods for Manufacturing Micro-Polarizers" filed on Jun. 11, 1990.Methods and apparatus for producing spatially-multiplexed images of 3-Dobjects are disclosed in copending U.S. application Ser. No. 08/126,077entitled "Method and Apparatus for Recording and Displaying SpatiallyMultiplexed Images of 3-D Objects for Stereoscopic Viewing Thereof"filed Sep. 23, 1993; and application Ser. No. 07/976,518 entitled"Method and Apparatus for Producing and Recording Spatially-MultiplexedImages for Use in 3-D Stereoscopic Viewing Thereof" filed Nov. 16, 1992.Each of these copending applications by Applicant is hereby incorporatedby reference in its entirety as if set forth fully herein.

In the illustrative embodiment, optically-transparent polarizing lenses112A and 112B are mounted within the frame 112C of polarized glasses111. During stereoscopic viewing of images displayed or projected fromcomputer system 1', the viewer wears polarized glasses 111 as he or shewould wear conventional eyeglasses. When worn on a viewer's head,polarizing lens 112A is positioned adjacent to the left eye of a viewer,while the second optically transparent element 112B is positionedadjacent to the right eye of the viewer. Polarizing lens 112A ischaracterized by the first polarization state P₁ so as to permit theleft eye of the viewer to view the first spatially modulated perspectiveimage displayed from the micropolarization panel, while substantiallypreventing the left eye of the view from viewing the second spatiallymodulated perspective image displayed from the micropolarization panel.Polarizing lens 112B is characterized by the second polarization stateP₂ so as to permit the right of the view to view the second spatiallymodulated perspective image displayed from the micropolarization panel,while substantially preventing the right eye of the viewer from viewingthe first spatially modulated perspective image displayed therefrom.This way, the viewer is capable of 3-D stereoscopic viewing of the 3-Dobject without "cross-viewing" from adjacent visual channels establishedby the stereoscopic imaging scheme.

Using the above-described spatial-multiplexing technique and displaypanel assembly 10" or 10'", portable computer system 1' candirectly-display or project polarized spatially-multiplexed images of3-D objects for stereoscopic viewing through light-weight polarizedglasses that can be adapted to the aesthetics of the viewer.

Portable computer system 1' is configured for the projection viewingmode by first removing back panel 21' as shown in FIG. 9. Then thedisplay portion of the housing is placed over the light projectionwindow of the overhead projector, as shown in FIG. 10. In theillustrative embodiment, the base portion of the computer is permittedto extend vertically, by itself, or by a simple bracing device 92 thatcan be snapped onto the edge of the base and display portions of thecomputer system, as shown in FIG. 10A. In other embodiments of thepresent invention, the display portion of the computer system can bedetached from the base thereof, and connected therewith by a standardcommunication cable well known in the art. In this way, the displayportion of the computer system containing display panel assembly 10" or10'" can be placed on top of the lens panel of the overhead projector,while the heavier base portion can be conveniently located elsewheredetermined the user.

As shown in FIG. 10A, overhead projector 90 typically contains thefollowing components within housing 93: power supply 94, lamp 95,focusing reflector 96, focusing lens 97, and Fresnel lens 98. Imageprojection head 99 is supported over the light projection window 91 ofthe projector by way of an adjustable support comprising verticalsupport member 100 attached to housing base 93, and horizontal supportmember 101 to which image head projector is connected at one end, andthe vertical support member 100 is releasably connected at its otherend, as shown, by slide mechanism 102. Within image projection head 99,image projection lens 104 and plane mirror 105 are mounted at about 45degrees to the projection lens 104. The geometrical optics involved inthe projection viewing process are clearly described by the ray tracingshown in FIG. 10A.

When configured as shown in FIGS. 10 and 10A, the computer system of thesecond illustrative embodiment is operated in its projection viewingmode by turning on the power to lamp 95 by ON/OFF switch 106, and thenselecting the Projection Viewing Mode. In any embodiment of the presentinvention disclosed herein, selection of a Viewing Mode command can bemade by way of either a keyboard entry operation, or by selecting thecommand or its graphical icon in a pulled-down menu supported by eitherthe Macintosh System 7.1 operating system, the Microsoft Windowsoperating system, or like operating system. Alternatively, Viewing Modescan be selected by depressing designated switches accessible through thesystem housing.

As shown in FIGS. 12 to 12D, the portable computer-based system of thepresent invention can be realized as a portable image display systemshown incorporating any one of display panel constructions 10, 10', 10",and 10'" described above. As illustrated, portable image display system110 includes a picture-frame shaped housing 111 having lighttransmission apertures 111A and 111B, through which display panelconstruction 10, 10', 10", or 10'" is securely mounted. Preferably, thesystem components shown in FIG. 2, or their functional equivalents aremounted within portable housing 111 in a conventional manner. Whileimage display system 110 is capable of storing, and even generatingframes of color image data, image display system 110 is shown in thedrawings interfaced with an auxiliary computer system 112 by way of aconventional serial data communication cable 113. The function ofauxiliary computer 113 is to supply color image data (e.g. SMI data) toimage display system 110 for display in either its direct viewing mode,shown in FIG. 12A, or in its projection viewing mode, shown in FIG. 12B,using a slightly portable light projection device 60' of the presentinvention.

In FIG. 12A, image display system 110 is shown vertically supported on adesktop by way of a stand 114 that is hingedly connected to portablehousing 111. Stand 114 retracts against the side walls of housing 111during transport or storage, as shown in FIG. 12. In the direct viewingmode shown in FIG. 12A, rear housing panel 115 is snapped into placeover the rear light transmission aperture so that reflective surface 40'is disposed adjacent Fresnel lens panel 38 of display panel assembly10'. In the configuration shown in FIG. 12A, image display system 110can be used as a backlighting panel for backlighting slides,transparencies, film structures and the like. To enter the BacklightingViewing Mode, LCD panel 33 is deactivated, fluorescent tubes 27 and 28are driven, and no external electric fields are applied across PDLCpanels 25, 31 34, and 36. In this mode, rear panel 115 is in place and aplane of light having a uniform intensity distribution emanates from thedisplay surface of the display panel assembly. The plane of light passesthrough the slide, film structure or transparency placed over thedisplay surface, and is spatial intensity modulated and spectrallyfiltered thereby to display imagery graphically represented therein. Inthe Backlighting Viewing Mode, the slide, film structure or transparencyfunctions as a non-programmable spatial light mask placed over thebacklighting panel of the present invention.

As shown in FIG. 12B, image display system 110 is configured forprojection viewing by simply removing rear housing panel 115, arrangingportable light projection device 60' about the housing as shown, andthen selecting the Projection Viewing Command, as described above. Inthis embodiment of the present invention, portable light projectiondevice 60' is similar to light projection device 60 shown in FIG. 4,except for several minor modifications. First, portable light projectiondevice 60' and image display system 110 are designed so that thehousings of each are adapted to interfit into a single housing ofcompact construction, as shown in FIG. 12. Second, first housing portion61' is constructed similar to second housing portion 62, in that firsthousing portion 61' can be telescopically extended to a required heightby frictional engagement amongst sleeves 61A and 61B. Third, divergentpolarized light rays emerge from side wall 61C of first housing portion61' so that it can be directed through display panel assembly 10"without reflection off specularly reflective surface 40' on the insidesurface of rear housing panel 115.

Once configured as shown in FIG. 12B, portable light projection device60' is adjusted as follows. First, the height of first housing section61 is adjusted so that the optical axis of projection lens 78 in thefirst housing portion is aligned with the optical axis of Fresnel lenspanel 38 in display panel assembly 10". Then, the height of opticalplatform 80 in the second housing portion is adjusted so that theoptical axis of projection lens 82 in the second housing portion isaligned with the optical axis 117 of Fresnel lens 38. Finally, withpower supplied to light source 73 and light emitting therefrom, theposition of projection lens 82 along the optical axis of Fresnel lenspanel 38 is adjusted so that the images formed on the display surface ofby LCD panel 33 are projected onto viewing surface 89, as enlargedfocused SMI images.

As shown in FIGS. 13 to 13B, the portable computer-based system of thepresent invention can be realized as a portable pen-computing device. Inthe illustrative embodiment, portable pen-computing device 120 is acomputer-based system having a general system architecture, as shown inFIG. 2. In addition, however, it incorporates the display/touch-screenpanel assembly 121 illustrated in FIG. 13B in order to provide the samewith a pen-type mode of data entry, and direct and projection modes ofstereoscopically viewing 3-D objects. All of these system components aremounted within a hand-supportable housing 122 that has lighttransmission apertures 123A and 123B through which display/touch-screenpanel assembly is supported using conventional display panel mountingtechniques known in the art. A rear panel 124 snap-fits into place tocover rear light transmission aperture 123B during the direct viewingmode of operation, shown in phantom in FIG. 13. As shown in FIG. 13B,rear panel 124 supports specularly reflective layer 40"

As illustrated in FIG. 13A, optically transparent touch-screen/displaypanel 121 panel comprises a number of components, namely: display panelconstruction 10, 10', 10" or 10'" (preferably 10"); a writing panel 126having first and second surfaces 126A and 126B, respectively; a basepanel 127 having first and second surfaces 127A and 127B, respectively;a plurality of optically transparent ultra-thin conductive strips 128applied to the second surface 127A of base panel 127 in a spaced apartmanner on the order of inter-pixel spacing of a suitable spatialresolution; an optically transparent conductive layer 129 applied to thesecond surface 126B of the writing panel; and a non-conductive viscousgel 130 disposed between and electrically isolating the writing panelfrom the base panel. As shown, the second surface of base panel 127B isdirectly affixed to the display surface of LCD panel 33 of the displaypanel assembly. Writing surface 126A is exposed to the ambientenvironment.

The writing panel 126 is made of flexible optically transparentmaterial, such as Mylar, which elastically deforms in response to theapplication of pressure on writing surface 126A by, for example, awriting stylus 131 moved thereover during conventional writingoperations by its user. Preferably, base panel 127 is made from anoptically transparent material such as glass, although other materialsmay be used without significantly compromised performance.Non-conductive gel 130 contains microscopic spheres 132 made ofsubstantially non-conductive material, such as plastic, and are free tomove within non-conductive gel 130 in response to the application ofpressure by writing stylus 131.

As shown in FIG. 13A, each optically transparent conductive strip 128extends parallel to every other optically transparent conductive stripand each such conductive strip is preassigned a correspondingx-coordinate value along the x-coordinate direction of the 2-D arrayrepresented along the writing surface. The y-coordinate direction in the2-D array extends along each optically transparent conductive strip.

Whenever the stylus is moved over the writing surface, the pressure pathformed therealong at each instant in time, elastically deforms thewriting surface, and causes the plastic microspheres to move away fromunder the tip of the writing stylus. This permits a selected one of theoptically transparent conductive strips 128 to momentarily establishcontact with optically transparent conductive layer 129 and in responseto the voltage applied across strips 128 and conductive layer 129, asmall electrical current to flows therebetween. A scanning mechanism 133is operably associated with the conductive strips and conductive layer,to cyclically determine, at each scanning interval, the x-coordinatevalue associated with the optically transparent conductive strip thatestablishes contact with the optically transparent conductive layer. Thescanning mechanism also measures the small electrical current flowassociated with the established electrical contact. Using this smallcurrent measure, the scanning mechanism computes the resistanceassociated with the circuit formed by the point of electrical contactbeneath the elastically deformable writing surface. Then, using apreconstructed resistance/y-coordinate look-up table, the computedresistance measure is converted into a corresponding y coordinate valueon the writing surface. For each X,Y coordinate pair assembled asdescribed above, the processor is able to construct an image data set ofthe graphical pattern that was traced out on the writing surface over aspecified time interval. This image data set is stored in bit-mappedform in memory (e.g. VRAM) for subsequent display using display panelassembly 10 of the portable pen-computing device of the presentinvention.

Having described the method and apparatus of the present invention withreference to the above illustrative embodiments, several modificationsreadily come to mind

In particular, as illustrated in FIGS. 14 and 14A, the light panel ofthe present invention can be realized without the use ofpolymer-dispersed liquid crystal(PDLC) technology. In this alternativeembodiment, a flat display panel is constructed by affixing conventionalLCD panel 33 to the front surface of light panel 140, which utilizesprinciples of electroluminescence, rather than disruption of totalinternal reflection, in order to emit light from the light panel duringthe light emission state thereof.

As illustrated in FIGS. 14 and 14A, in particular, the flat displaypanel of this particular embodiment uses an electroluminescent structurehaving both light emissive and light transmissive modes of operationwhich, as will be explained above in connection with the otherembodiments, are electronically selectable during direct viewing andprojection viewing modes of operation, respectively.

As best illustrated in FIG. 14A, light panel 140 can be formed bydepositing a thin layer of optically transparent conducting material141, such as Indium Tin Oxide(ITO) or gold foil, about 20 to 30Angstroms thick, on a thin optically transparent (support) panel 142, toform a first optically transparent electrode layer thereon. Thereafter,a layer of optically transparent material 143, such as the oxides ofaluminum niobium tantalum, is deposited over optically transparentelectrode layer 142 and panel 141. Using depositing techniques wellknown in the art, a layer of electroluminescent material 144 having ahigh energy-band gap (e.g. greater than 73.0 electron volts) between itsconduction and valence bands, such as aluminum dioxide 8.4 electronvolts, is deposited over the optically transparent electrode layer 143.The reason that the electroluminescent material must have such a highenergy-band gap between its conduction and valence bands is that thiscondition ensures that the layer of electroluminescent material isoptically transparent when the operating voltage (i.e. electric field)is not applied thereacross, and yet emits light when an electric fieldis applied. Then, a layer of Indium Tin Oxide 145 is applied to a secondoptically transparent panel 146. Finally, optically transparent panels141 and 146 are brought together so that electroluminescent layer 144comes in intimate electrical contact with electrode layer 145, andelectroluminescent light panel 140 of integral construction is therebyformed. To the front surface of panel 146, LCD panel 33 is affixed inconventional manner. To the rear surface of panel 142, Fresnel lenspanel 147 is affixed in a similar manner described above in connectionwith the other embodiments of the present invention.

During the direct viewing mode, an external electric field is appliedacross electrode layers 141 and 145, and in response thereto electronsare excited to the conduction band of electroluminescent material 143and permitted to drop to the valence band thereof, whereby photons areemitted having wavelengths in the visible portion of the electromagneticspectrum. Details regarding the physics of the electroluminescent panelhereof during its emission mode are generally described in the paperentitled "Diffraction-grating-enhanced light emission from tunneljunctions" by J. R. Kirtley, et al., published in Applied PhysicalLetters, Volume 37, No. 5, Sep. 1, 1980, which is incorporated herein byreference. In the direct viewing mode, the reflective layer adjacentFresnel lens panel 148 functions to reflect light in the direction ofLCD panel 133. In general, the intensity distribution of the lightemitted from the light panel during this mode of operation issubstantially uniform in the x and y coordinate directions, and thusintensity compensation measures are not required.

During the projection viewing mode, no voltage (i.e. electric field) isapplied across electrode layers 141 and 145, the light panel 140 isoperated in its light transmission state and thus layer 141 andelectroluminescent layer 144 are each optically transparent and do notpresent significant light diffraction or scattering. In the projectionviewing mode, rear panel 21' is removed away from Fresnel lens panel 147and an external source of light, such as from device 60, is projectedthrough the entire flat display panel assembly. In its lighttransmission state, the projected light rays are first focused byFresnel lens panel 147 and thereafter pass completely through theelectroluminescent panel without substantial scattering or absorption ofthe light rays. Thereafter, the focused light rays are spatial intensitymodulated by LCD panel 33 and after passing through a projection lens,as described hereinabove, are ultimately projected onto a wall surfaceor projection screen for large field viewing.

In other embodiments of the present invention, flat display panel 140can be mounted beneath optically transparent writing panel 126,described above, to provide a novel writing/display panel for use in avariety of pen computing applications.

In yet other embodiments of the present invention, micropolarizationpanel 110 can be affixed to the front display surface of LCD panel 33 ofwriting panel 126, to permit stereoscopic viewing of spatiallymultiplexed images.

As illustrated in FIGS. 15, 15A and 15B, it is also possible to combinethe inventive features of the portable computer system 1 and lightprojection device 60 disclosed herein and thereby produce a lightweight,transportable computer system 1" of integrated construction having bothdirect and projection viewing modes of operation. The primary advantageof this novel construction is that it avoids altogether the use ofportable light projection devices as well as overhead projectors.

As shown in FIG. 15, the computer system 1" is similar in all respectswith the computer system 1 of the first illustrative embodiment shown inFIG. 4, except that the base portion 2" of the housing is extendedslightly in the rearward directions in order to embody the polarizedlight source 73, reflector lens 74, polarizing filter 77 and lightfocusing/projecting lens 78, as shown. In addition, a light transmissionaperture 201 is formed in the top surface of the rear extension portionof computer system base 2" and is selectively coverable by a hingedaperture cover 202, as shown in FIG. 15.

As shown in FIGS. 15, 15A and 15B, an image projection lens assembly 203is used with computer system 1" during its projection viewing mode ofoperation. As shown, image projection device 203 comprises a thin imageprojection lens 204 supported in a lens frame 205, from which a supportstem 206 extends. Preferably, the lens frame and support stem arerealized as a integral unit, fabricated from a lightweight plastic.Notably, the focal lengths of image projection lens 204 and Fresnel lenspanel 38 are selected so that video images are projected onto a remoteprojection surface (e.g. image plane 84) typically located at least 10or more feet from the computer system.

During transport and direct viewing modes of operation, the imageprojection lens assembly 203 is safely housed within a vacant storagecompartment 207 formed in the central lower portion of the computersystem base, as shown in FIGS. 15 and 15A. In general, the physicaldimensions of storage compartment 207 are slightly greater than thephysical dimensions of the projection lens assembly. An access opening207A is formed in the front of computer system base to provide access tostorage compartment 207, as shown in FIG. 15A. To store the projectionlens assembly, all that is necessarily is to slide the stem portion ofthe assembly into the access opening 207A, as shown in FIG. 15A, andpush it thereinto until it is completely accommodated by the walls ofthe storage compartment. To remove the projection lens assembly, thereverse operations are performed. As shown in FIG. 15B, the projectionlens is mounted along the projection axis of the Fresnel lens panel 38by inserting the end of stem portion 206 into stem mounting slot 208formed in the edge of the computer system base.

During the projection viewing mode of operation, the computer system 1"is configured as shown in FIG. 15. In this configuration, aperture cover202 is arranged in its open configuration and projection lens 204 ismounted along the projection axis of the Fresnel lens panel 38. Thecomputer system is induced in its projection viewing mode and videosignals are provided to the pixel drivers of the display panel assembly.As polarized light rays are produced from internal light source 73, theyare reflected off light reflective surface 40 on rear housing panel 21and projected through the display panel assembly 10. Simultaneously, thepolarized light rays are spatial intensity modulated in accordance withthe video signals driving the pixel drivers and focused by Fresnel lenspanel 38 onto the principal plane of image projection lens 205 supportedalong the projection axis thereof. The focused color images formed atthe principal plane of projection lens 205 are then projected onto aremote projection display surface located at a predetermined distanceaway from the computer system. The projection display surface may be awall surface, a projection display screen or like surface.Alternatively, image projection lens 205 may be adapted with an imagefocusing adjustment mechanism 210 that permits projection lens 205 to besimply translated along the projection axis of Fresnel lens 38 in orderto adjust the focal distance, and thus the projection plane onto whichprojected color images are to be projected by computer system 1" in itsprojection viewing mode. This feature permits the computer system 1" toproject in-focus color images onto electrically passive surfaces locatedat a broad range of distances from the display panel thereof.

During the direct viewing mode, the computer system 1" is reconfiguredso that the image projection lens assembly is dismounted and storedwithin the storage compartment 207. The display panel assembly 10 isinduced in its direct viewing mode. The viewer is permitted to viewdisplayed imagery directly from the display surface of the display panelin a conventional manner. Preferably, the computer system 1" is adaptedfor multi-media presentations, combining both video and sound in bothdirect and projection viewing modes of operation.

In FIGS. 16 and 17, two alternative embodiments of the transportableimage projection system hereof are schematicatically illustrated. Likethe other illustrative embodiments disclosed herein, these transportableimage projection systems employ the electro-optical light panel of thepresent invention to realize a transportable system having both directand projection viewing modes of operation. During the direct viewingmode of operation, spatially-multiplexed images (SMIs) can be displayedon the surface of the electro-optical light panel of the system for usein stereoscopic 3-D viewing through a pair of polarization eyeglasses,such as polarizing eyeglasses 111 shown in FIGS. 12A and 12B. During itsprojection viewing mode of operation, SMIs can be projected onto aremotely situated projection viewing screen 89 for stereoscopic 3-Dviewing through polarization eyeglasses 111. As will become apparenthereinafter, the image display systems of these alterntive embodimentscan be used in virtually any environment where direct or projectionviewing is desired or required.

As shown in FIG. 16, image display system 300 comprises a transportablehousing 301 having a light transmission aperture 302 and an interiorvolume 303 within which the various optical and electro-opticalcomponents of system are configured to carry out the objects of thepresent invention. In this illstrative embodiment, any one of theelectro-optical panel assemblies shown in FIGS. 5A, 5B, 11A, 11B, 12Cand 12D (hereinafter collectively denoted by "10") is mounted within oradjacent light transmission aperture 302 by way of conventional panelmounting techniques. As described in great detail hereinabove, each ofone there electro-optical panel assemblies has a plurality of PDLC lightdiffusing panels, which have light-scattering and light non-scatteringstates of operation selectable under electronic control.

As shown in FIG. 16, a light projection system 304 is mounted behind theelectro-optical panel assembly 10, within the transportable housing.Light projection system 304 can be realized by arranging, for example,optical elements 73, 74, 77 and 78 as shown in FIG. 4B. The imagedisplay system of FIG. 16 also includes a system controller 305 forproducing control signals used to control light projection system 304and electro-optical display panel 10. Stereoscopic 3-D viewingcapablities are provided to the image display system of FIG. 16 byaffixing a retardation-based micropolarization panel 110B to the surfaceof the LCD panel, and providing viewers polarizing eyeglasses 11 throughwhich to view micropolarized SMIs displayed in either the direct orprojection viewing mode. The selection of the focal distances forprojection lens 78 and Fresnel lens 38 will be made by considering thefunctions that must be achieved during the direct and projection viewingmodes when using the electro-optical display panel 10, or variationthereof.

When the image display system of FIG. 16 is operated in its directviewing mode, light projection system 304 focuses polarized light raysonto the electro-optical panel assembly 10 while the PDLC lightdiffusing panels thereof diffusely scatter these polarized light raysand the LCD panel 33 spatial intensity modulate the diffusely scatteredlight rays. 10. These functions can be achieved by realizing thefollowing conditions. During the direct viewing mode, PDLC lightdiffusing panels of electro-optical panel assembly 10 are operated intheir light non-scattering state of operation. The focal distance ofprojection lens 78 is selected to equal the distance between theprincipal lens of projection lens 78 and the principal plane of Fresnellens 38. Also, the focal distance of Fresnel lens 38 is selected to berelatively long in comparision with the focal distance of projectionlens 78 so that Fresnel lens 38 has little effect on the light raysbeing directly viewed by a viewer positioned closely adjacent thedisplay panel during the direct viewing mode.

When the image display system of FIG. 16 is operated in its projectionviewing mode, the projection lens within light projection system 304cooperates with the Fresnel lens panel within electro-optical panelassembly 10 to focus polarized light rays onto projection displaysurface 89. During this mode of operation, the PDLC light diffusingpanels within electro-optical panel assembly 10 are operated in theirlight transmissive, non-scattering mode so that they transmit, withoutscattering, projected light rays while the LCD panel of electro-opticalpanel assembly 10 spatial intensity modulates the same before beingprojected onto projection display surface 89. In order to correctly viewimages displayed on the projection display screen during the projectionviewing mode, image inverter 306 is used to process the pixel drivesignals provided to the LCD panel during the spatial intensitymodulation (i.e. image formation) process so that viewers may correctlyview imagery being display on projection screen 89. Image inverter 306can be readily realized using computer software or logic circuitry in amanner known in the art.

The stereoscopic image display system shown in FIG. 17 can be obtainedby modifying the image display system of FIG. 16 in a number ofrespects. As will be apparent below, the resulting image display systemis characterized by a simplier, more efficient construction.

As shown in FIG. 17, image display system 300' comprises: housing 301and light transmission aperture 302; a simplified electro-optical lightpanel assembly 10"" consisting of only plexiglass support substrate 25',PDLC light diffusing panel 31, and micropolarization panel 110B shown inFIG. 11B, assembled together in the named order to form an integraldisplay panel structure having a projection axis normal to its displaysurface; an image projector 307 (e.g. the Model CPJ-100 LCD Projectorfrom the SONY Corporation, of Tokyo, Japan, or a state-of-the art photoslide-film projector) mounted within the housing along the projectionaxis of electro-optical light panel assembly 10""; a variablefocal-distance projection lens system 308 mounted within the housingbetween the image projector 307 and electro-optical light panel assembly10"", for projecting focused image to a first focal distance f(dv) inthe direct viewing mode, and for projecting focused image to a second,substantially longer focal distance f(pv) in the projection viewingmode; an image inverter 309 (e.g. VCD drive signal processor for theCPJ-100 LCD Projector, and image inversion optics for thestate-of-the-art photoslide-film projector) for inverting projectedimages so that they are correctly viewed from left-to-right andright-to-left on projection display screen 89; and amicroprocessor-realized system controller 305' for producing controlsignals that are used to control the state of operation of the imageprojector 307, the variable focal-distance projection lens system 308,the electro-optical light panel assembly 10"" and image invertor 309during direct and projection modes of operation. Stereoscopic 3-Dviewing capablities are provided to the image display system of FIG. 17by affixing a retardation-based micropolarization panel 110B to thesurface of the LCD panel within the CPJ-100 LCD Projector, or to thesurface of film-slides to be viewed, depending on which embodiment ofthe image projector is being realized, and providing viewers polarizingeyeglasses 111 through which micropolarized SMIs can be viewed in eitherthe direct or projection mode.

When the image display system of FIG. 17 is operated in its directviewing mode, the electrically-addressable LCD panel within the CPJ-100LCD Projector, or the film structure of film slide being viewed, spatialintensity modulates projected light rays, while variable-focusprojection lens system 308 focuses the spatial-intensity modulated lightrays onto the PDLC light diffusing panel 31 of electro-optical panelassembly 10"" which diffusely scatters such rays to form a focused imagethereupon for directly viewing by a nearly viewer. Then when the imagedisplay system of FIG. 17 is operated in its projection viewing mode,the electrically-addressable LCD panel within the CPJ-100 LCD Projector,or the film structure of film slide being viewed, spatial intensitymodulates light rays projected towards the electro-optical light panelassembly 10"", and variable-focus projection lens system 308 focuses thespatial-intensity modulated light rays onto projection display surface89, while the PDLC light diffusing panel of electro-optical light panelassembly 10"" allows projected light rays to be transmitted therethroughwith minimal light scattering. These functions are achieved as follows.In the direct viewing mode, the system controller 305' sets the focaldistance of variable-focus projection lens system 308 to equal thedistance between the principal plane of projection lens system and theprincipal plane of the PDLC light diffusing panel within electro-opticallight panel assembly 10"", while operating the PDLC light diffusingpanel in its light scattering state. In the projection viewing mode, thesystem controller 305' sets the focal distance of variable-focusprojection lens system 308 to equal the distance between the principalplane of projection lens system 308 and projection display surface 89,while operating the PDLC light diffusing panel of electro-optical lightpanel assembly 10"" in its light non-scattering state and operatingimage invertor 309 so that projected images are correctly displayed(i.e. from left-to-right and vice versa) on projection display surface89.

For purposes of clarity, the various information storage and processingfacilities shown in FIG. 2 have not been explicitly shown in FIGS. 16and 17. It is understood, however, that such functionalities can andwill typically be embodied within image display systems 300 and 300'described in great detail above.

The modifications to the various aspects of the present inventiondescribed above are merely exemplary. It is understood that othermodifications to the illustrative embodiments will readily occur topersons with ordinary skill in the art. All such modifications andvariations are deemed to be within the scope and spirit of the presentinvention as defined by the accompanying Claims to Invention.

What is claimed is:
 1. An image display system having direct andprojection viewing modes, comprising:light producing structure forproducing light during said direct and projection viewing modes; anelectro-optical panel having a first optical state during which light istransmitted therethrough with substantial scattering and a secondoptical state during which light is transmitted therethrough withoutsubstantial scattering; a spatial light modulation structure forspatially modulating the intensity of light produced from said lightproducing structure during said direct viewing mode and during saidprojection viewing mode; and an optical state selector for selecting thefirst optical state of said electro-optical panel during said directviewing mode, and the second optical state of said electro-optical panelduring said projection viewing mode; wherein during said direct viewingmode, light produced from said light producing structure is scattered bysaid electro-optical panel and spatial intensity modulated by saidspatial light modulation structure to form a first image for directviewing; and wherein during said projection viewing mode, light producedfrom said light producing structure is transmitted through saidelectro-optical panel without substantial scattering and spatialintensity modulated by said spatial light modulation structure to form asecond image for projection onto a projection display surface forprojection viewing.
 2. The image display system of claim 1, wherein saidspatial light modulation structure is an electrically-addressablespatial light modulation panel.
 3. The image display system of claim 2,wherein said electro-optical panel is disposed between said lightproducing structure and said electrically-addressable spatial lightmodulation panel.
 4. The image display system of claim 3, wherein saidelectro-optical panel and said electrically-addressable spatial lightmodulation panel are mounted together to form an integrated displaypanel assembly.
 5. The image display system of claim 4, which furthercomprises a micropolarization panel mounted onto saidelectrically-addressable spatial light modulation panel formicropolarizing spatially multiplexed images displayed in either saiddirect or projection viewing mode.
 6. The image display system of claim2, wherein said electro-optical panel comprises a polymer-dispersedliquid crystal (PDLC) panel having optically transparent electrodesurfaces.
 7. The image display system of claim 2, which furthercomprises a thin light focusing panel disposed closely adjacent to saidelectrically-addressable spatial light modulation panel, for focusingspatial intensity modulated light onto said projection display surfacelocated at a predetermined focal plane during said projection viewingmode.
 8. The image display panel of claim 7, wherein said thin lightfocusing panel is an optical element selected from the group consistingof a holographic lens panel and a Fresnel lens panel.
 9. The imagedisplay system of claim 2, wherein said electrically-addressable spatiallight modulation panel comprises an active-matrix LCD panel.
 10. Theimage display system of claim 9, wherein said light producing structureproduces light having a polarization state which is employed by saidactive-matrix LCD panel.
 11. The image display system of claim 1,wherein said spatial light modulation structure is disposed near saidlight producing structure.
 12. The image display system of claim 11,wherein said spatial light modulation structure is anelectrically-addressable spatial light modulation panel disposed betweensaid light producing structure and said electro-optical panel.
 13. Theimage display system of claim 11, which further comprises avariable-focus projection lens system disposed near said spatial lightmodulation structure, said variable-focus projection lens system havingat least a first focal distance for focusing spatial intensity modulatedlight from said spatial light modulation panel onto said electro-opticalpanel during said projection viewing mode, and a second focal distancefor projecting spatial intensity modulated light from said spatial lightmodulation structure through said electro-optical panel, onto saidprojection display surface located at said second focal distance, duringsaid projection viewing mode.
 14. The image display system of claim 12,which further comprises a micropolarization panel mounted onto saidelectrically-addressable spatial light modulation panel formicropolarizing spatially multiplexed images displayed in either saiddirect or projection viewing mode.
 15. The image display system of claim14, wherein said electrically-addressable spatial light modulation paneland said micropolarization panel are mounted together to form anintegrated electro-optical structure.
 16. The image display system ofclaim 13, wherein said electro-optical panel comprises apolymer-dispersed liquid crystal (PDLC) panel having opticallytransparent electrode surfaces.
 17. The image display system of claim12, wherein said electrically-addressable spatial light modulation panelcomprises an active-matrix LCD panel.
 18. The image display system ofclaim 17, wherein said light producing structure produces light having apolarization state which is employed by said active-matrix LCD panel.19. The image display system of claim 1, which further comprises atransportable housing of compact construction having an interior volumewithin which the components of the system are enclosed, and a lighttransmission aperture through which spatial intensity modulated lightcan be transmitted during said direct and projection viewing modes. 20.The image display system of claim 11, wherein said spatial lightmodulation structure is a slide-film structure to be viewed.